tests/test-setdiscovery.t

transaction: quietly rollback if no other changes than temporary files

If no actual change have been made, we don't really need to roll them back. We
only have to cleanup some temporary files and it seems reasonable to do that
quietly.

This will help us to use the transaction in wider context¹ without impacting the
user experience.

[1] as in Python context managers that lives longer.

Function to test discovery between two repos in both directions, using both the local shortcut
(which is currently not activated by default) and the full remotable protocol:

  $ testdesc() { # revs_a, revs_b, dagdesc
  >     if [ -d foo ]; then rm -rf foo; fi
  >     hg init foo
  >     cd foo
  >     hg debugbuilddag "$3"
  >     hg clone . a $1 --quiet
  >     hg clone . b $2 --quiet
  >     echo
  >     echo "% -- a -> b tree"
  >     hg -R a debugdiscovery b --verbose --old
  >     echo
  >     echo "% -- a -> b set"
  >     hg -R a debugdiscovery b --verbose --debug --config progress.debug=true
  >     echo
  >     echo "% -- a -> b set (tip only)"
  >     hg -R a debugdiscovery b --verbose --debug --config progress.debug=true --rev tip
  >     echo
  >     echo "% -- b -> a tree"
  >     hg -R b debugdiscovery a --verbose --old
  >     echo
  >     echo "% -- b -> a set"
  >     hg -R b debugdiscovery a --verbose --debug --config progress.debug=true
  >     echo
  >     echo "% -- b -> a set (tip only)"
  >     hg -R b debugdiscovery a --verbose --debug --config progress.debug=true --rev tip
  >     cd ..
  > }


Small superset:

  $ testdesc '-ra1 -ra2' '-rb1 -rb2 -rb3' '
  > +2:f +1:a1:b1
  > <f +4 :a2
  > +5 :b2
  > <f +3 :b3'
  
  % -- a -> b tree
  comparing with b
  searching for changes
  unpruned common: 01241442b3c2 66f7d451a68b b5714e113bc0
  elapsed time:  * seconds (glob)
  round-trips:                   4
  queries:                       6
    queries-branches:            2
    queries-between:             4
  heads summary:
    total common heads:          2
      also local heads:          2
      also remote heads:         1
      both:                      1
    local heads:                 2
      common:                    2
      missing:                   0
    remote heads:                3
      common:                    1
      unknown:                   2
  local changesets:              7
    common:                      7
      heads:                     2
      roots:                     1
    missing:                     0
      heads:                     0
      roots:                     0
    first undecided set:         3
      heads:                     1
      roots:                     1
      common:                    3
      missing:                   0
  common heads: 01241442b3c2 b5714e113bc0
  
  % -- a -> b set
  comparing with b
  query 1; heads
  searching for changes
  all local changesets known remotely
  elapsed time:  * seconds (glob)
  round-trips:                   1
  queries:                       2
  heads summary:
    total common heads:          2
      also local heads:          2
      also remote heads:         1
      both:                      1
    local heads:                 2
      common:                    2
      missing:                   0
    remote heads:                3
      common:                    1
      unknown:                   2
  local changesets:              7
    common:                      7
      heads:                     2
      roots:                     1
    missing:                     0
      heads:                     0
      roots:                     0
    first undecided set:         3
      heads:                     1
      roots:                     1
      common:                    3
      missing:                   0
  common heads: 01241442b3c2 b5714e113bc0
  
  % -- a -> b set (tip only)
  comparing with b
  query 1; heads
  searching for changes
  all local changesets known remotely
  elapsed time:  * seconds (glob)
  round-trips:                   1
  queries:                       1
  heads summary:
    total common heads:          1
      also local heads:          1
      also remote heads:         0
      both:                      0
    local heads:                 2
      common:                    1
      missing:                   1
    remote heads:                3
      common:                    0
      unknown:                   3
  local changesets:              7
    common:                      6
      heads:                     1
      roots:                     1
    missing:                     1
      heads:                     1
      roots:                     1
    first undecided set:         6
      heads:                     2
      roots:                     1
      common:                    5
      missing:                   1
  common heads: b5714e113bc0
  
  % -- b -> a tree
  comparing with a
  searching for changes
  unpruned common: 01241442b3c2 b5714e113bc0
  elapsed time:  * seconds (glob)
  round-trips:                   1
  queries:                       0
    queries-branches:            0
    queries-between:             0
  heads summary:
    total common heads:          2
      also local heads:          1
      also remote heads:         2
      both:                      1
    local heads:                 3
      common:                    1
      missing:                   2
    remote heads:                2
      common:                    2
      unknown:                   0
  local changesets:             15
    common:                      7
      heads:                     2
      roots:                     1
    missing:                     8
      heads:                     2
      roots:                     2
    first undecided set:         8
      heads:                     2
      roots:                     2
      common:                    0
      missing:                   8
  common heads: 01241442b3c2 b5714e113bc0
  
  % -- b -> a set
  comparing with a
  query 1; heads
  searching for changes
  all remote heads known locally
  elapsed time:  * seconds (glob)
  round-trips:                   1
  queries:                       3
  heads summary:
    total common heads:          2
      also local heads:          1
      also remote heads:         2
      both:                      1
    local heads:                 3
      common:                    1
      missing:                   2
    remote heads:                2
      common:                    2
      unknown:                   0
  local changesets:             15
    common:                      7
      heads:                     2
      roots:                     1
    missing:                     8
      heads:                     2
      roots:                     2
    first undecided set:         8
      heads:                     2
      roots:                     2
      common:                    0
      missing:                   8
  common heads: 01241442b3c2 b5714e113bc0
  
  % -- b -> a set (tip only)
  comparing with a
  query 1; heads
  searching for changes
  all remote heads known locally
  elapsed time:  * seconds (glob)
  round-trips:                   1
  queries:                       1
  heads summary:
    total common heads:          2
      also local heads:          1
      also remote heads:         2
      both:                      1
    local heads:                 3
      common:                    1
      missing:                   2
    remote heads:                2
      common:                    2
      unknown:                   0
  local changesets:             15
    common:                      7
      heads:                     2
      roots:                     1
    missing:                     8
      heads:                     2
      roots:                     2
    first undecided set:         8
      heads:                     2
      roots:                     2
      common:                    0
      missing:                   8
  common heads: 01241442b3c2 b5714e113bc0


Many new:

  $ testdesc '-ra1 -ra2' '-rb' '
  > +2:f +3:a1 +3:b
  > <f +30 :a2'
  
  % -- a -> b tree
  comparing with b
  searching for changes
  unpruned common: bebd167eb94d
  elapsed time:  * seconds (glob)
  round-trips:                   4
  queries:                       3
    queries-branches:            1
    queries-between:             2
  heads summary:
    total common heads:          1
      also local heads:          1
      also remote heads:         0
      both:                      0
    local heads:                 2
      common:                    1
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             35
    common:                      5
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        34
      heads:                     2
      roots:                     1
      common:                    4
      missing:                  30
  common heads: bebd167eb94d
  
  % -- a -> b set
  comparing with b
  query 1; heads
  searching for changes
  taking initial sample
  searching: 2 queries
  query 2; still undecided: 29, sample size is: 29
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      31
  heads summary:
    total common heads:          1
      also local heads:          1
      also remote heads:         0
      both:                      0
    local heads:                 2
      common:                    1
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             35
    common:                      5
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        34
      heads:                     2
      roots:                     1
      common:                    4
      missing:                  30
  common heads: bebd167eb94d
  
  % -- a -> b set (tip only)
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 31, sample size is: 31
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      32
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 2
      common:                    0
      missing:                   2
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             35
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    33
      heads:                     2
      roots:                     2
    first undecided set:        35
      heads:                     2
      roots:                     1
      common:                    2
      missing:                  33
  common heads: 66f7d451a68b
  
  % -- b -> a tree
  comparing with a
  searching for changes
  unpruned common: 66f7d451a68b bebd167eb94d
  elapsed time:  * seconds (glob)
  round-trips:                   6
  queries:                       5
    queries-branches:            1
    queries-between:             4
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         1
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                2
      common:                    1
      unknown:                   1
  local changesets:              8
    common:                      5
      heads:                     1
      roots:                     1
    missing:                     3
      heads:                     1
      roots:                     1
    first undecided set:         3
      heads:                     1
      roots:                     1
      common:                    0
      missing:                   3
  common heads: bebd167eb94d
  
  % -- b -> a set
  comparing with a
  query 1; heads
  searching for changes
  taking initial sample
  searching: 2 queries
  query 2; still undecided: 2, sample size is: 2
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                       3
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         1
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                2
      common:                    1
      unknown:                   1
  local changesets:              8
    common:                      5
      heads:                     1
      roots:                     1
    missing:                     3
      heads:                     1
      roots:                     1
    first undecided set:         3
      heads:                     1
      roots:                     1
      common:                    0
      missing:                   3
  common heads: bebd167eb94d
  
  % -- b -> a set (tip only)
  comparing with a
  query 1; heads
  searching for changes
  taking initial sample
  searching: 2 queries
  query 2; still undecided: 2, sample size is: 2
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                       3
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         1
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                2
      common:                    1
      unknown:                   1
  local changesets:              8
    common:                      5
      heads:                     1
      roots:                     1
    missing:                     3
      heads:                     1
      roots:                     1
    first undecided set:         3
      heads:                     1
      roots:                     1
      common:                    0
      missing:                   3
  common heads: bebd167eb94d

Both sides many new with stub:

  $ testdesc '-ra1 -ra2' '-rb' '
  > +2:f +2:a1 +30 :b
  > <f +30 :a2'
  
  % -- a -> b tree
  comparing with b
  searching for changes
  unpruned common: 2dc09a01254d
  elapsed time:  * seconds (glob)
  round-trips:                   6
  queries:                       5
    queries-branches:            1
    queries-between:             4
  heads summary:
    total common heads:          1
      also local heads:          1
      also remote heads:         0
      both:                      0
    local heads:                 2
      common:                    1
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             34
    common:                      4
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        33
      heads:                     2
      roots:                     1
      common:                    3
      missing:                  30
  common heads: 2dc09a01254d
  
  % -- a -> b set
  comparing with b
  query 1; heads
  searching for changes
  taking initial sample
  searching: 2 queries
  query 2; still undecided: 29, sample size is: 29
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      31
  heads summary:
    total common heads:          1
      also local heads:          1
      also remote heads:         0
      both:                      0
    local heads:                 2
      common:                    1
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             34
    common:                      4
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        33
      heads:                     2
      roots:                     1
      common:                    3
      missing:                  30
  common heads: 2dc09a01254d
  
  % -- a -> b set (tip only)
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 31, sample size is: 31
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      32
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 2
      common:                    0
      missing:                   2
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             34
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    32
      heads:                     2
      roots:                     2
    first undecided set:        34
      heads:                     2
      roots:                     1
      common:                    2
      missing:                  32
  common heads: 66f7d451a68b
  
  % -- b -> a tree
  comparing with a
  searching for changes
  unpruned common: 2dc09a01254d 66f7d451a68b
  elapsed time:  * seconds (glob)
  round-trips:                   6
  queries:                       5
    queries-branches:            1
    queries-between:             4
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         1
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                2
      common:                    1
      unknown:                   1
  local changesets:             34
    common:                      4
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        30
      heads:                     1
      roots:                     1
      common:                    0
      missing:                  30
  common heads: 2dc09a01254d
  
  % -- b -> a set
  comparing with a
  query 1; heads
  searching for changes
  taking initial sample
  searching: 2 queries
  query 2; still undecided: 29, sample size is: 29
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      30
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         1
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                2
      common:                    1
      unknown:                   1
  local changesets:             34
    common:                      4
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        30
      heads:                     1
      roots:                     1
      common:                    0
      missing:                  30
  common heads: 2dc09a01254d
  
  % -- b -> a set (tip only)
  comparing with a
  query 1; heads
  searching for changes
  taking initial sample
  searching: 2 queries
  query 2; still undecided: 29, sample size is: 29
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      30
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         1
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                2
      common:                    1
      unknown:                   1
  local changesets:             34
    common:                      4
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        30
      heads:                     1
      roots:                     1
      common:                    0
      missing:                  30
  common heads: 2dc09a01254d


Both many new:

  $ testdesc '-ra' '-rb' '
  > +2:f +30 :b
  > <f +30 :a'
  
  % -- a -> b tree
  comparing with b
  searching for changes
  unpruned common: 66f7d451a68b
  elapsed time:  * seconds (glob)
  round-trips:                   6
  queries:                       5
    queries-branches:            1
    queries-between:             4
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             32
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        32
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  30
  common heads: 66f7d451a68b
  
  % -- a -> b set
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 31, sample size is: 31
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      32
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             32
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        32
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  30
  common heads: 66f7d451a68b
  
  % -- a -> b set (tip only)
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 31, sample size is: 31
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      32
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             32
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        32
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  30
  common heads: 66f7d451a68b
  
  % -- b -> a tree
  comparing with a
  searching for changes
  unpruned common: 66f7d451a68b
  elapsed time:  * seconds (glob)
  round-trips:                   6
  queries:                       5
    queries-branches:            1
    queries-between:             4
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             32
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        32
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  30
  common heads: 66f7d451a68b
  
  % -- b -> a set
  comparing with a
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 31, sample size is: 31
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      32
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             32
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        32
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  30
  common heads: 66f7d451a68b
  
  % -- b -> a set (tip only)
  comparing with a
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 31, sample size is: 31
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      32
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             32
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        32
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  30
  common heads: 66f7d451a68b


Both many new skewed:

  $ testdesc '-ra' '-rb' '
  > +2:f +30 :b
  > <f +50 :a'
  
  % -- a -> b tree
  comparing with b
  searching for changes
  unpruned common: 66f7d451a68b
  elapsed time:  * seconds (glob)
  round-trips:                   6
  queries:                       5
    queries-branches:            1
    queries-between:             4
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             52
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    50
      heads:                     1
      roots:                     1
    first undecided set:        52
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  50
  common heads: 66f7d451a68b
  
  % -- a -> b set
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 51, sample size is: 51
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      52
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             52
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    50
      heads:                     1
      roots:                     1
    first undecided set:        52
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  50
  common heads: 66f7d451a68b
  
  % -- a -> b set (tip only)
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 51, sample size is: 51
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      52
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             52
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    50
      heads:                     1
      roots:                     1
    first undecided set:        52
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  50
  common heads: 66f7d451a68b
  
  % -- b -> a tree
  comparing with a
  searching for changes
  unpruned common: 66f7d451a68b
  elapsed time:  * seconds (glob)
  round-trips:                   5
  queries:                       4
    queries-branches:            1
    queries-between:             3
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             32
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        32
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  30
  common heads: 66f7d451a68b
  
  % -- b -> a set
  comparing with a
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 31, sample size is: 31
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      32
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             32
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        32
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  30
  common heads: 66f7d451a68b
  
  % -- b -> a set (tip only)
  comparing with a
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 31, sample size is: 31
  2 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   2
  queries:                      32
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:             32
    common:                      2
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:        32
      heads:                     1
      roots:                     1
      common:                    2
      missing:                  30
  common heads: 66f7d451a68b


Both many new on top of long history:

  $ testdesc '-ra' '-rb' '
  > +1000:f +30 :b
  > <f +50 :a'
  
  % -- a -> b tree
  comparing with b
  searching for changes
  unpruned common: 7ead0cba2838
  elapsed time:  * seconds (glob)
  round-trips:                   6
  queries:                       5
    queries-branches:            1
    queries-between:             4
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:           1050
    common:                   1000
      heads:                     1
      roots:                     1
    missing:                    50
      heads:                     1
      roots:                     1
    first undecided set:      1050
      heads:                     1
      roots:                     1
      common:                 1000
      missing:                  50
  common heads: 7ead0cba2838
  
  % -- a -> b set
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 1049, sample size is: 11
  sampling from both directions
  searching: 3 queries
  query 3; still undecided: 31, sample size is: 31
  3 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   3
  queries:                      43
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:           1050
    common:                   1000
      heads:                     1
      roots:                     1
    missing:                    50
      heads:                     1
      roots:                     1
    first undecided set:      1050
      heads:                     1
      roots:                     1
      common:                 1000
      missing:                  50
  common heads: 7ead0cba2838
  
  % -- a -> b set (tip only)
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 1049, sample size is: 11
  sampling from both directions
  searching: 3 queries
  query 3; still undecided: 31, sample size is: 31
  3 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   3
  queries:                      43
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:           1050
    common:                   1000
      heads:                     1
      roots:                     1
    missing:                    50
      heads:                     1
      roots:                     1
    first undecided set:      1050
      heads:                     1
      roots:                     1
      common:                 1000
      missing:                  50
  common heads: 7ead0cba2838
  
  % -- b -> a tree
  comparing with a
  searching for changes
  unpruned common: 7ead0cba2838
  elapsed time:  * seconds (glob)
  round-trips:                   5
  queries:                       4
    queries-branches:            1
    queries-between:             3
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:           1030
    common:                   1000
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:      1030
      heads:                     1
      roots:                     1
      common:                 1000
      missing:                  30
  common heads: 7ead0cba2838
  
  % -- b -> a set
  comparing with a
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 1029, sample size is: 11
  sampling from both directions
  searching: 3 queries
  query 3; still undecided: 15, sample size is: 15
  3 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   3
  queries:                      27
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:           1030
    common:                   1000
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:      1030
      heads:                     1
      roots:                     1
      common:                 1000
      missing:                  30
  common heads: 7ead0cba2838
  
  % -- b -> a set (tip only)
  comparing with a
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 1029, sample size is: 11
  sampling from both directions
  searching: 3 queries
  query 3; still undecided: 15, sample size is: 15
  3 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   3
  queries:                      27
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                 1
      common:                    0
      missing:                   1
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:           1030
    common:                   1000
      heads:                     1
      roots:                     1
    missing:                    30
      heads:                     1
      roots:                     1
    first undecided set:      1030
      heads:                     1
      roots:                     1
      common:                 1000
      missing:                  30
  common heads: 7ead0cba2838


One with >200 heads. We now switch to send them all in the initial roundtrip, but still do sampling for the later request.

  $ hg init manyheads
  $ cd manyheads
  $ echo "+300:r @a" >dagdesc
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3 *r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3*r+3" >>dagdesc # 20 heads
  $ echo "@b *r+3" >>dagdesc # one more head
  $ hg debugbuilddag <dagdesc
  reading DAG from stdin

  $ hg heads -t --template . | wc -c
  \s*261 (re)

  $ hg clone -b a . a
  adding changesets
  adding manifests
  adding file changes
  added 1340 changesets with 0 changes to 0 files (+259 heads)
  new changesets 1ea73414a91b:1c51e2c80832
  updating to branch a
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg clone -b b . b
  adding changesets
  adding manifests
  adding file changes
  added 304 changesets with 0 changes to 0 files
  new changesets 1ea73414a91b:513314ca8b3a
  updating to branch b
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg -R a debugdiscovery b --debug --verbose --config progress.debug=true --config devel.discovery.randomize=false  --config devel.discovery.sample-size.initial=50
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 1080, sample size is: 50
  sampling from both directions
  searching: 3 queries
  query 3; still undecided: 1030, sample size is: 200
  sampling from both directions
  searching: 4 queries
  query 4; still undecided: 547, sample size is: 210
  sampling from both directions
  searching: 5 queries
  query 5; still undecided: 336, sample size is: 220
  sampling from both directions
  searching: 6 queries
  query 6; still undecided: 114, sample size is: 114
  6 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   6
  queries:                    1054
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:               260
      common:                    0
      missing:                 260
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:           1340
    common:                    300
      heads:                     1
      roots:                     1
    missing:                  1040
      heads:                   260
      roots:                   260
    first undecided set:      1340
      heads:                   260
      roots:                     1
      common:                  300
      missing:                1040
  common heads: 3ee37d65064a
  $ hg -R a debugdiscovery b --debug --verbose --config progress.debug=true --rev tip
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  searching: 2 queries
  query 2; still undecided: 303, sample size is: 9
  sampling from both directions
  searching: 3 queries
  query 3; still undecided: 3, sample size is: 3
  3 total queries in *.????s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   3
  queries:                      13
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:               260
      common:                    0
      missing:                 260
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:           1340
    common:                    300
      heads:                     1
      roots:                     1
    missing:                  1040
      heads:                   260
      roots:                   260
    first undecided set:      1340
      heads:                   260
      roots:                     1
      common:                  300
      missing:                1040
  common heads: 3ee37d65064a

  $ hg -R a debugdiscovery b --debug --config devel.discovery.exchange-heads=false --config devel.discovery.randomize=false --config devel.discovery.grow-sample.rate=1.20 --config devel.discovery.sample-size=50
  comparing with b
  searching for changes
  sampling from both directions
  query 1; still undecided: 1340, sample size is: 50
  sampling from both directions
  query 2; still undecided: 995, sample size is: 60
  sampling from both directions
  query 3; still undecided: 913, sample size is: 72
  sampling from both directions
  query 4; still undecided: 816, sample size is: 204
  sampling from both directions
  query 5; still undecided: 612, sample size is: 153
  sampling from both directions
  query 6; still undecided: 456, sample size is: 123
  sampling from both directions
  query 7; still undecided: 332, sample size is: 147
  sampling from both directions
  query 8; still undecided: 184, sample size is: 176
  sampling from both directions
  query 9; still undecided: 8, sample size is: 8
  9 total queries in *s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   9
  queries:                     993
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:               260
      common:                    0
      missing:                 260
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:           1340
    common:                    300
      heads:                     1
      roots:                     1
    missing:                  1040
      heads:                   260
      roots:                   260
    first undecided set:      1340
      heads:                   260
      roots:                     1
      common:                  300
      missing:                1040
  common heads: 3ee37d65064a

Test actual protocol when pulling one new head in addition to common heads

  $ hg clone -U b c
  $ hg -R c id -ir tip
  513314ca8b3a
  $ hg -R c up -qr default
  $ touch c/f
  $ hg -R c ci -Aqm "extra head"
  $ hg -R c id -i
  e64a39e7da8b

  $ hg serve -R c -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
  $ cat hg.pid >> $DAEMON_PIDS

  $ hg -R b incoming http://localhost:$HGPORT/ -T '{node|short}\n'
  comparing with http://localhost:$HGPORT/
  searching for changes
  e64a39e7da8b

  $ killdaemons.py
  $ cut -d' ' -f6- access.log | grep -v cmd=known # cmd=known uses random sampling
  "GET /?cmd=capabilities HTTP/1.1" 200 -
  "GET /?cmd=batch HTTP/1.1" 200 - x-hgarg-1:cmds=heads+%3Bknown+nodes%3D513314ca8b3ae4dac8eec56966265b00fcf866db x-hgproto-1:0.1 0.2 comp=$USUAL_COMPRESSIONS$ partial-pull
  "GET /?cmd=getbundle HTTP/1.1" 200 - x-hgarg-1:$USUAL_BUNDLE_CAPS$&cg=1&common=513314ca8b3ae4dac8eec56966265b00fcf866db&heads=e64a39e7da8b0d54bc63e81169aff001c13b3477 x-hgproto-1:0.1 0.2 comp=$USUAL_COMPRESSIONS$ partial-pull
  "GET /?cmd=listkeys HTTP/1.1" 200 - x-hgarg-1:namespace=phases x-hgproto-1:0.1 0.2 comp=$USUAL_COMPRESSIONS$ partial-pull
  $ cat errors.log

  $ cd ..


Issue 4438 - test coverage for 3ef893520a85 issues.

  $ mkdir issue4438
  $ cd issue4438
#if false
generate new bundles:
  $ hg init r1
  $ for i in `"$PYTHON" $TESTDIR/seq.py 101`; do hg -R r1 up -qr null && hg -R r1 branch -q b$i && hg -R r1 ci -qmb$i; done
  $ hg clone -q r1 r2
  $ for i in `"$PYTHON" $TESTDIR/seq.py 10`; do hg -R r1 up -qr null && hg -R r1 branch -q c$i && hg -R r1 ci -qmc$i; done
  $ hg -R r2 branch -q r2change && hg -R r2 ci -qmr2change
  $ hg -R r1 bundle -qa $TESTDIR/bundles/issue4438-r1.hg
  $ hg -R r2 bundle -qa $TESTDIR/bundles/issue4438-r2.hg
#else
use existing bundles:
  $ hg init r1
  $ hg -R r1 -q unbundle $TESTDIR/bundles/issue4438-r1.hg
  $ hg -R r1 -q up
  $ hg init r2
  $ hg -R r2 -q unbundle $TESTDIR/bundles/issue4438-r2.hg
  $ hg -R r2 -q up
#endif

Set iteration order could cause wrong and unstable results - fixed in 73cfaa348650:

  $ hg -R r1 outgoing r2 -T'{rev} '
  comparing with r2
  searching for changes
  101 102 103 104 105 106 107 108 109 110  (no-eol)

The case where all the 'initialsamplesize' samples already were common would
give 'all remote heads known locally' without checking the remaining heads -
fixed in 86c35b7ae300:

  $ cat >> r1/.hg/hgrc << EOF
  > [devel]
  > discovery.randomize = False
  > EOF

  $ hg -R r1 outgoing r2 -T'{rev} ' --config extensions.blackbox= \
  > --config blackbox.track='command commandfinish discovery'
  comparing with r2
  searching for changes
  101 102 103 104 105 106 107 108 109 110  (no-eol)
  $ hg -R r1 --config extensions.blackbox= blackbox --config blackbox.track=
  * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> serve --no-profile --cmdserver chgunix * (glob) (chg !)
  * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> -R r1 outgoing r2 *-T{rev} * --config *extensions.blackbox=* (glob)
  * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> found 101 common and 1 unknown server heads, 1 roundtrips in *.????s (glob)
  * @5d0b986a083e0d91f116de4691e2aaa54d5bbec0 (*)> -R r1 outgoing r2 *-T{rev} * --config *extensions.blackbox=* exited 0 after *.?? seconds (glob)
  $ cd ..

Even if the set of revs to discover is restricted, unrelated revs may be
returned as common heads.

  $ mkdir ancestorsof
  $ cd ancestorsof
  $ hg init a
  $ hg clone a b -q
  $ cd b
  $ hg debugbuilddag '.:root *root *root'
  $ hg log -G -T '{node|short}'
  o  fa942426a6fd
  |
  | o  66f7d451a68b
  |/
  o  1ea73414a91b
  
  $ hg push -r 66f7d451a68b -q
  $ hg debugdiscovery --verbose --rev fa942426a6fd
  comparing with $TESTTMP/ancestorsof/a
  searching for changes
  elapsed time:  * seconds (glob)
  round-trips:                   1
  queries:                       1
  heads summary:
    total common heads:          1
      also local heads:          1
      also remote heads:         1
      both:                      1
    local heads:                 2
      common:                    1
      missing:                   1
    remote heads:                1
      common:                    1
      unknown:                   0
  local changesets:              3
    common:                      2
      heads:                     1
      roots:                     1
    missing:                     1
      heads:                     1
      roots:                     1
    first undecided set:         1
      heads:                     1
      roots:                     1
      common:                    0
      missing:                   1
  common heads: 66f7d451a68b

  $ cd ..


Test debuging discovery using different subset of the same repository
=====================================================================

remote is a local subset
------------------------

remote will be last 25 heads of the local graph

  $ cd $TESTTMP/manyheads
  $ hg -R a debugdiscovery \
  > --debug \
  > --remote-as-revs 'last(heads(all()), 25)' \
  > --config devel.discovery.randomize=false
  query 1; heads
  searching for changes
  all remote heads known locally
  elapsed time:  * seconds (glob)
  round-trips:                   1
  queries:                     260
  heads summary:
    total common heads:         25
      also local heads:         25
      also remote heads:        25
      both:                     25
    local heads:               260
      common:                   25
      missing:                 235
    remote heads:               25
      common:                   25
      unknown:                   0
  local changesets:           1340
    common:                    400
      heads:                    25
      roots:                     1
    missing:                   940
      heads:                   235
      roots:                   235
    first undecided set:       940
      heads:                   235
      roots:                   235
      common:                    0
      missing:                 940
  common heads: 0dfd965d91c6 0fe09b60448d 14a17233ce9d 175c0a3072cf 1c51e2c80832 1e51600e0698 24eb5f9bdbab 25ce09526613 36bd00abde57 426989fdefa0 596d87362679 5dd1039ea5c0 5ef24f022278 5f230dc19419 80b39998accb 88f40688ffb5 9e37ddf8c632 abf4d55b075e b2ce801fddfe b368b6ac3ce3 c959bf2e869c c9fba6ba4e2e d783207cf649 d9a51e256f21 e3717a4e3753

local is a local subset
------------------------

remote will be last 25 heads of the local graph

  $ cd $TESTTMP/manyheads
  $ hg -R a debugdiscovery b \
  > --debug \
  > --local-as-revs 'first(heads(all()), 25)' \
  > --config devel.discovery.randomize=false
  comparing with b
  query 1; heads
  searching for changes
  taking quick initial sample
  query 2; still undecided: 375, sample size is: 81
  sampling from both directions
  query 3; still undecided: 3, sample size is: 3
  3 total queries *s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   3
  queries:                     109
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                25
      common:                    0
      missing:                  25
    remote heads:                1
      common:                    0
      unknown:                   1
  local changesets:            400
    common:                    300
      heads:                     1
      roots:                     1
    missing:                   100
      heads:                    25
      roots:                    25
    first undecided set:       400
      heads:                    25
      roots:                     1
      common:                  300
      missing:                 100
  common heads: 3ee37d65064a

both local and remove are subset
------------------------

remote will be last 25 heads of the local graph

  $ cd $TESTTMP/manyheads
  $ hg -R a debugdiscovery \
  > --debug \
  > --local-as-revs 'first(heads(all()), 25)' \
  > --remote-as-revs 'last(heads(all()), 25)' \
  > --config devel.discovery.randomize=false
  query 1; heads
  searching for changes
  taking quick initial sample
  query 2; still undecided: 375, sample size is: 81
  sampling from both directions
  query 3; still undecided: 3, sample size is: 3
  3 total queries in *s (glob)
  elapsed time:  * seconds (glob)
  round-trips:                   3
  queries:                     109
  heads summary:
    total common heads:          1
      also local heads:          0
      also remote heads:         0
      both:                      0
    local heads:                25
      common:                    0
      missing:                  25
    remote heads:               25
      common:                    0
      unknown:                  25
  local changesets:            400
    common:                    300
      heads:                     1
      roots:                     1
    missing:                   100
      heads:                    25
      roots:                    25
    first undecided set:       400
      heads:                    25
      roots:                     1
      common:                  300
      missing:                 100
  common heads: 3ee37d65064a

Test -T json output
-------------------

  $ hg -R a debugdiscovery \
  > -T json \
  > --debug \
  > --local-as-revs 'first(heads(all()), 25)' \
  > --remote-as-revs 'last(heads(all()), 25)' \
  > --config devel.discovery.randomize=false
  [
   {
    "elapsed": *, (glob)
    "nb-common-heads": 1,
    "nb-common-heads-both": 0,
    "nb-common-heads-local": 0,
    "nb-common-heads-remote": 0,
    "nb-common-roots": 1,
    "nb-head-local": 25,
    "nb-head-local-missing": 25,
    "nb-head-remote": 25,
    "nb-head-remote-unknown": 25,
    "nb-ini_und": 400,
    "nb-ini_und-common": 300,
    "nb-ini_und-heads": 25,
    "nb-ini_und-missing": 100,
    "nb-ini_und-roots": 1,
    "nb-missing-heads": 25,
    "nb-missing-roots": 25,
    "nb-revs": 400,
    "nb-revs-common": 300,
    "nb-revs-missing": 100,
    "output": "query 1; heads\nsearching for changes\ntaking quick initial sample\nquery 2; still undecided: 375, sample size is: 81\nsampling from both directions\nquery 3; still undecided: 3, sample size is: 3\n3 total queries in *s\n", (glob)
    "total-queries": 109,
    "total-roundtrips": 3
   }
  ]