view tests/test-rebase-inmemory.t @ 42406:f385ba70e4af

changelog: optionally store added and removed files in changeset extras

As mentioned in an earlier patch, copies._chain() is used a lot in the
changeset-centric version of pathcopies(). It is expensive because it
needs to look at the manifest in order to filter out copies whose
target file has since been removed. I want to store the sets of added
and removed files in the changeset in order to speed that up. This
patch does the writing part of that. It could easily be a separate
config, but it's currently tied to experimental.copies.write-to since
that's the only real use case (it will also make the {file_*} template
keywords faster, but I doubt that anyone cares enough about those to
write extra metadata for them).

The new information is stored in the changeset extras. Since they're
always subsets of the changeset's "files" list, they're stored as
indexes into that list. I've stored the indexes as stringified ints
separated by NUL bytes. The size of 00changelog.d for the hg repo
increased in size by 0.28% percent (compared to the size with only
copy information in the changesets, which in turn is 0.17% larger than
without copy information). We could store only the delta between the
indexes and we could store them in binary, but the chosen format is
more readable.

We could also have implemented this as a cache outside the
changelog. One advantage of doing it that way is that we would get the
speedups from the {file_*} template keywords also on old
repos. Another advantage is that it we can rewrite the cache if we
find a bug in how we calculate the set of files. A disadvantage is
that it would be more complex. Another is that it would surely use
more space. We already write the copy information to the changeset
extras, so it seems like a small step to also write these file sets.

Differential Revision: https://phab.mercurial-scm.org/D6416

#require symlink execbit
  $ cat << EOF >> $HGRCPATH
  > [phases]
  > publish=False
  > [extensions]
  > amend=
  > rebase=
  > debugdrawdag=$TESTDIR/drawdag.py
  > strip=
  > [rebase]
  > experimental.inmemory=1
  > [diff]
  > git=1
  > [alias]
  > tglog = log -G --template "{rev}: {node|short} '{desc}'\n"
  > EOF

Rebase a simple DAG:
  $ hg init repo1
  $ cd repo1
  $ hg debugdrawdag <<'EOS'
  > c b
  > |/
  > d
  > |
  > a
  > EOS
  $ hg up -C a
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg tglog
  o  3: 814f6bd05178 'c'
  |
  | o  2: db0e82a16a62 'b'
  |/
  o  1: 02952614a83d 'd'
  |
  @  0: b173517d0057 'a'
  
  $ hg cat -r 3 c
  c (no-eol)
  $ hg cat -r 2 b
  b (no-eol)
  $ hg rebase --debug -r b -d c | grep rebasing
  rebasing in-memory
  rebasing 2:db0e82a16a62 "b" (b)
  $ hg tglog
  o  3: ca58782ad1e4 'b'
  |
  o  2: 814f6bd05178 'c'
  |
  o  1: 02952614a83d 'd'
  |
  @  0: b173517d0057 'a'
  
  $ hg cat -r 3 b
  b (no-eol)
  $ hg cat -r 2 c
  c (no-eol)
  $ cd ..

Case 2:
  $ hg init repo2
  $ cd repo2
  $ hg debugdrawdag <<'EOS'
  > c b
  > |/
  > d
  > |
  > a
  > EOS

Add a symlink and executable file:
  $ hg up -C c
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ ln -s somefile e
  $ echo f > f
  $ chmod +x f
  $ hg add e f
  $ hg amend -q
  $ hg up -Cq a

Write files to the working copy, and ensure they're still there after the rebase
  $ echo "abc" > a
  $ ln -s def b
  $ echo "ghi" > c
  $ echo "jkl" > d
  $ echo "mno" > e
  $ hg tglog
  o  3: f56b71190a8f 'c'
  |
  | o  2: db0e82a16a62 'b'
  |/
  o  1: 02952614a83d 'd'
  |
  @  0: b173517d0057 'a'
  
  $ hg cat -r 3 c
  c (no-eol)
  $ hg cat -r 2 b
  b (no-eol)
  $ hg cat -r 3 e
  somefile (no-eol)
  $ hg rebase --debug -s b -d a | grep rebasing
  rebasing in-memory
  rebasing 2:db0e82a16a62 "b" (b)
  $ hg tglog
  o  3: fc055c3b4d33 'b'
  |
  | o  2: f56b71190a8f 'c'
  | |
  | o  1: 02952614a83d 'd'
  |/
  @  0: b173517d0057 'a'
  
  $ hg cat -r 2 c
  c (no-eol)
  $ hg cat -r 3 b
  b (no-eol)
  $ hg rebase --debug -s 1 -d 3 | grep rebasing
  rebasing in-memory
  rebasing 1:02952614a83d "d" (d)
  rebasing 2:f56b71190a8f "c"
  $ hg tglog
  o  3: 753feb6fd12a 'c'
  |
  o  2: 09c044d2cb43 'd'
  |
  o  1: fc055c3b4d33 'b'
  |
  @  0: b173517d0057 'a'
  
Ensure working copy files are still there:
  $ cat a
  abc
  $ readlink.py b
  b -> def
  $ cat e
  mno

Ensure symlink and executable files were rebased properly:
  $ hg up -Cq 3
  $ readlink.py e
  e -> somefile
  $ ls -l f | cut -c -10
  -rwxr-xr-x

Rebase the working copy parent
  $ hg up -C 3
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg rebase -r 3 -d 0 --debug | grep rebasing
  rebasing in-memory
  rebasing 3:753feb6fd12a "c" (tip)
  $ hg tglog
  @  3: 844a7de3e617 'c'
  |
  | o  2: 09c044d2cb43 'd'
  | |
  | o  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  

Test reporting of path conflicts

  $ hg rm a
  $ mkdir a
  $ touch a/a
  $ hg ci -Am "a/a"
  adding a/a
  $ hg tglog
  @  4: daf7dfc139cb 'a/a'
  |
  o  3: 844a7de3e617 'c'
  |
  | o  2: 09c044d2cb43 'd'
  | |
  | o  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  
  $ hg rebase -r . -d 2
  rebasing 4:daf7dfc139cb "a/a" (tip)
  saved backup bundle to $TESTTMP/repo2/.hg/strip-backup/daf7dfc139cb-fdbfcf4f-rebase.hg

  $ hg tglog
  @  4: c6ad37a4f250 'a/a'
  |
  | o  3: 844a7de3e617 'c'
  | |
  o |  2: 09c044d2cb43 'd'
  | |
  o |  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  
  $ echo foo > foo
  $ hg ci -Aqm "added foo"
  $ hg up '.^'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo bar > bar
  $ hg ci -Aqm "added bar"
  $ hg rm a/a
  $ echo a > a
  $ hg ci -Aqm "added a back!"
  $ hg tglog
  @  7: 855e9797387e 'added a back!'
  |
  o  6: d14530e5e3e6 'added bar'
  |
  | o  5: 9b94b9373deb 'added foo'
  |/
  o  4: c6ad37a4f250 'a/a'
  |
  | o  3: 844a7de3e617 'c'
  | |
  o |  2: 09c044d2cb43 'd'
  | |
  o |  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  
  $ hg rebase -r . -d 5
  rebasing 7:855e9797387e "added a back!" (tip)
  saved backup bundle to $TESTTMP/repo2/.hg/strip-backup/855e9797387e-81ee4c5d-rebase.hg

  $ hg tglog
  @  7: bb3f02be2688 'added a back!'
  |
  | o  6: d14530e5e3e6 'added bar'
  | |
  o |  5: 9b94b9373deb 'added foo'
  |/
  o  4: c6ad37a4f250 'a/a'
  |
  | o  3: 844a7de3e617 'c'
  | |
  o |  2: 09c044d2cb43 'd'
  | |
  o |  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  
  $ mkdir -p c/subdir
  $ echo c > c/subdir/file.txt
  $ hg add c/subdir/file.txt
  $ hg ci -m 'c/subdir/file.txt'
  $ hg rebase -r . -d 3 -n
  starting dry-run rebase; repository will not be changed
  rebasing 8:e147e6e3c490 "c/subdir/file.txt" (tip)
  abort: error: 'c/subdir/file.txt' conflicts with file 'c' in 3.
  [255]
  $ hg rebase -r 3 -d . -n
  starting dry-run rebase; repository will not be changed
  rebasing 3:844a7de3e617 "c"
  abort: error: file 'c' cannot be written because  'c/' is a directory in e147e6e3c490 (containing 1 entries: c/subdir/file.txt)
  [255]

  $ cd ..

Test path auditing (issue5818)

  $ mkdir lib_
  $ ln -s lib_ lib
  $ hg init repo
  $ cd repo
  $ mkdir -p ".$TESTTMP/lib"
  $ touch ".$TESTTMP/lib/a"
  $ hg add ".$TESTTMP/lib/a"
  $ hg ci -m 'a'

  $ touch ".$TESTTMP/lib/b"
  $ hg add ".$TESTTMP/lib/b"
  $ hg ci -m 'b'

  $ hg up -q '.^'
  $ touch ".$TESTTMP/lib/c"
  $ hg add ".$TESTTMP/lib/c"
  $ hg ci -m 'c'
  created new head
  $ hg rebase -s 1 -d .
  rebasing 1:* "b" (glob)
  saved backup bundle to $TESTTMP/repo/.hg/strip-backup/*-rebase.hg (glob)
  $ cd ..

Test dry-run rebasing

  $ hg init repo3
  $ cd repo3
  $ echo a>a
  $ hg ci -Aqma
  $ echo b>b
  $ hg ci -Aqmb
  $ echo c>c
  $ hg ci -Aqmc
  $ echo d>d
  $ hg ci -Aqmd
  $ echo e>e
  $ hg ci -Aqme

  $ hg up 1 -q
  $ echo f>f
  $ hg ci -Amf
  adding f
  created new head
  $ echo g>g
  $ hg ci -Aqmg
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Make sure it throws error while passing --continue or --abort with --dry-run
  $ hg rebase -s 2 -d 6 -n --continue
  abort: cannot specify both --dry-run and --continue
  [255]
  $ hg rebase -s 2 -d 6 -n --abort
  abort: cannot specify both --dry-run and --abort
  [255]

Check dryrun gives correct results when there is no conflict in rebasing
  $ hg rebase -s 2 -d 6 -n
  starting dry-run rebase; repository will not be changed
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  dry-run rebase completed successfully; run without -n/--dry-run to perform this rebase

  $ hg diff
  $ hg status

  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Check dryrun working with --collapse when there is no conflict
  $ hg rebase -s 2 -d 6 -n --collapse
  starting dry-run rebase; repository will not be changed
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  dry-run rebase completed successfully; run without -n/--dry-run to perform this rebase

Check dryrun gives correct results when there is conflict in rebasing
Make a conflict:
  $ hg up 6 -q
  $ echo conflict>e
  $ hg ci -Aqm "conflict with e"
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  7:d2c195b28050 test
  |  conflict with e
  |
  o  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
  $ hg rebase -s 2 -d 7 -n
  starting dry-run rebase; repository will not be changed
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  merging e
  transaction abort!
  rollback completed
  hit a merge conflict
  [1]
  $ hg diff
  $ hg status
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  7:d2c195b28050 test
  |  conflict with e
  |
  o  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Check dryrun working with --collapse when there is conflicts
  $ hg rebase -s 2 -d 7 -n --collapse
  starting dry-run rebase; repository will not be changed
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  merging e
  hit a merge conflict
  [1]

In-memory rebase that fails due to merge conflicts

  $ hg rebase -s 2 -d 7
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  merging e
  transaction abort!
  rollback completed
  hit merge conflicts; re-running rebase without in-memory merge
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  merging e
  warning: conflicts while merging e! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]
  $ hg rebase --abort
  saved backup bundle to $TESTTMP/repo3/.hg/strip-backup/c1e524d4287c-f91f82e1-backup.hg
  rebase aborted

Retrying without in-memory merge won't lose working copy changes
  $ cd ..
  $ hg clone repo3 repo3-dirty -q
  $ cd repo3-dirty
  $ echo dirty > a
  $ hg rebase -s 2 -d 7
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  merging e
  transaction abort!
  rollback completed
  hit merge conflicts; re-running rebase without in-memory merge
  abort: uncommitted changes
  [255]
  $ cat a
  dirty

Retrying without in-memory merge won't lose merge state
  $ cd ..
  $ hg clone repo3 repo3-merge-state -q
  $ cd repo3-merge-state
  $ hg merge 4
  merging e
  warning: conflicts while merging e! (edit, then use 'hg resolve --mark')
  2 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
  [1]
  $ hg resolve -l
  U e
  $ hg rebase -s 2 -d 7
  rebasing 2:177f92b77385 "c"
  abort: outstanding merge conflicts
  [255]
  $ hg resolve -l
  U e

==========================
Test for --confirm option|
==========================
  $ cd ..
  $ hg clone repo3 repo4 -q
  $ cd repo4
  $ hg strip 7 -q
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Check it gives error when both --dryrun and --confirm is used:
  $ hg rebase -s 2 -d . --confirm --dry-run
  abort: cannot specify both --confirm and --dry-run
  [255]
  $ hg rebase -s 2 -d . --confirm --abort
  abort: cannot specify both --confirm and --abort
  [255]
  $ hg rebase -s 2 -d . --confirm --continue
  abort: cannot specify both --confirm and --continue
  [255]

Test --confirm option when there are no conflicts:
  $ hg rebase -s 2 -d . --keep --config ui.interactive=True --confirm << EOF
  > n
  > EOF
  starting in-memory rebase
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  rebase completed successfully
  apply changes (yn)? n
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
  $ hg rebase -s 2 -d . --keep --config ui.interactive=True --confirm << EOF
  > y
  > EOF
  starting in-memory rebase
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  rebase completed successfully
  apply changes (yn)? y
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  o  9:9fd28f55f6dc test
  |  e
  |
  o  8:12cbf031f469 test
  |  d
  |
  o  7:c83b1da5b1ae test
  |  c
  |
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Test --confirm option when there is a conflict
  $ hg up tip -q
  $ echo ee>e
  $ hg ci --amend -m "conflict with e" -q
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  9:906d72f66a59 test
  |  conflict with e
  |
  o  8:12cbf031f469 test
  |  d
  |
  o  7:c83b1da5b1ae test
  |  c
  |
  o  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
  $ hg rebase -s 4 -d . --keep --confirm
  starting in-memory rebase
  rebasing 4:e860deea161a "e"
  merging e
  hit a merge conflict
  [1]
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  9:906d72f66a59 test
  |  conflict with e
  |
  o  8:12cbf031f469 test
  |  d
  |
  o  7:c83b1da5b1ae test
  |  c
  |
  o  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Test a metadata-only in-memory merge
  $ cd $TESTTMP
  $ hg init no_exception
  $ cd no_exception
# Produce the following graph:
#   o  'add +x to foo.txt'
#   | o  r1  (adds bar.txt, just for something to rebase to)
#   |/
#   o  r0   (adds foo.txt, no +x)
  $ echo hi > foo.txt
  $ hg ci -qAm r0
  $ echo hi > bar.txt
  $ hg ci -qAm r1
  $ hg co -qr ".^"
  $ chmod +x foo.txt
  $ hg ci -qAm 'add +x to foo.txt'
issue5960: this was raising an AttributeError exception
  $ hg rebase -r . -d 1
  rebasing 2:539b93e77479 "add +x to foo.txt" (tip)
  saved backup bundle to $TESTTMP/no_exception/.hg/strip-backup/*.hg (glob)
  $ hg diff -c tip
  diff --git a/foo.txt b/foo.txt
  old mode 100644
  new mode 100755

Test rebasing a commit with copy information, but no content changes

  $ cd ..
  $ hg clone -q repo1 merge-and-rename
  $ cd merge-and-rename
  $ cat << EOF >> .hg/hgrc
  > [experimental]
  > evolution.createmarkers=True
  > evolution.allowunstable=True
  > EOF
  $ hg co -q 1
  $ hg mv d e
  $ hg ci -qm 'rename d to e'
  $ hg co -q 3
  $ hg merge -q 4
  $ hg ci -m 'merge'
  $ hg co -q 2
  $ mv d e
  $ hg addremove -qs 0
  $ hg ci -qm 'untracked rename of d to e'
  $ hg debugobsolete -q `hg log -T '{node}' -r 4` `hg log -T '{node}' -r .`
  1 new orphan changesets
  $ hg tglog
  @  6: 676538af172d 'untracked rename of d to e'
  |
  | *    5: 71cb43376053 'merge'
  | |\
  | | x  4: 2c8b5dad7956 'rename d to e'
  | | |
  | o |  3: ca58782ad1e4 'b'
  |/ /
  o /  2: 814f6bd05178 'c'
  |/
  o  1: 02952614a83d 'd'
  |
  o  0: b173517d0057 'a'
  
  $ hg rebase -b 5 -d tip
  rebasing 3:ca58782ad1e4 "b"
  rebasing 5:71cb43376053 "merge"
  note: not rebasing 5:71cb43376053 "merge", its destination already has all its changes

  $ cd ..

Test rebasing a commit with copy information

  $ hg init rebase-rename
  $ cd rebase-rename
  $ echo a > a
  $ hg ci -Aqm 'add a'
  $ echo a2 > a
  $ hg ci -m 'modify a'
  $ hg co -q 0
  $ hg mv a b
  $ hg ci -qm 'rename a to b'
  $ hg rebase -d 1
  rebasing 2:b977edf6f839 "rename a to b" (tip)
  merging a and b to b
  saved backup bundle to $TESTTMP/rebase-rename/.hg/strip-backup/b977edf6f839-0864f570-rebase.hg
  $ hg st --copies --change .
  A b
    a
  R a
  $ cd ..

Rebase across a copy with --collapse

  $ hg init rebase-rename-collapse
  $ cd rebase-rename-collapse
  $ echo a > a
  $ hg ci -Aqm 'add a'
  $ hg mv a b
  $ hg ci -m 'rename a to b'
  $ hg co -q 0
  $ echo a2 > a
  $ hg ci -qm 'modify a'
  $ hg rebase -r . -d 1 --collapse
  rebasing 2:41c4ea50d4cf "modify a" (tip)
  merging b and a to b
  saved backup bundle to $TESTTMP/rebase-rename-collapse/.hg/strip-backup/41c4ea50d4cf-b90b7994-rebase.hg
  $ cd ..

Test rebasing when the file we are merging in destination is empty

  $ hg init test
  $ cd test
  $ echo a > foo
  $ hg ci -Aqm 'added a to foo'

  $ rm foo
  $ touch foo
  $ hg di
  diff --git a/foo b/foo
  --- a/foo
  +++ b/foo
  @@ -1,1 +0,0 @@
  -a

  $ hg ci -m "make foo an empty file"

  $ hg up '.^'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo b > foo
  $ hg di
  diff --git a/foo b/foo
  --- a/foo
  +++ b/foo
  @@ -1,1 +1,1 @@
  -a
  +b
  $ hg ci -m "add b to foo"
  created new head

  $ hg rebase -r . -d 1 --config ui.merge=internal:merge3
  rebasing 2:fb62b706688e "add b to foo" (tip)
  merging foo
  hit merge conflicts; re-running rebase without in-memory merge
  rebasing 2:fb62b706688e "add b to foo" (tip)
  merging foo
  warning: conflicts while merging foo! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]