tests/test-merge-types.t

simplemerge: stop merging file flags

As 384df4db6520 (merge: merge file flags together with file content,
2013-01-09) explains, we shouldn't do a 3-way merge of the
symlink. However, since 84614212ae39 (flags: actually merge flags in
simplemerge, 2020-05-16), we do that in
`simplemerge.simplemerge()`. What's more, the merging of the
executable flag there isn't actually necessary; it was made a no-op by
the very next commit, i.e. 4234c9af515d (flags: read flag from
dirstate/disk for workingcopyctx (issue5743), 2020-05-16).

I found the overall flag-merging code (not the bit in
`simplemerge.py`) very hard to follow, but I think I now finally
understand how it works. `mergestate.resolve()` calculates the merged
file flags and sets them on the local side of the merge (confusingly
by calling `_restore_backup()`). Then it calls
`filemerge.filemerge()`, which in turn calls
`simplemerge.simplemerge()` (if premerge is enabled). That means that
the flags on the local side `fcs.flags()` are already correct when the
flag-merging code in `simplemerge.simplemerge()` runs. Interestingly,
that code still works when the local side already has the merged
value, it just doesn't change the value. Here's a truth table to
explain why:

```
BLOMCAR
0000000
0011111
0101011
0111111
1000000
1010000
1100000
1111101
```

B: Base
L: Local
O: Other
M: Merged flags from `mergestate.resolve()`, i.e. what's called "local"
   when we get to `simplemerge.simplemerge()`
C: `commonflags` in `simplemerge.simplemerge()`, i.e. `M & O`
A: `addedflags` in `simplemerge.simplemerge()`, i.e. `(M ^ O) - B`
R: Re-merged flags `simplemerge.simplemerge()`, i.e. `C | A`

As you can see, the re-merged flags are always unchanged compared to
the initial merged flags (R equals M).

Therefore, this patch effectively backs out 84614212ae39. (I might
later refactor this code to have the flags explicitly passed in.)

`simplemerge.simplemerge()` is also called from
`contrib/simplemerge.py`, but that code never passes any flags.

Differential Revision: https://phab.mercurial-scm.org/D11879

#require symlink execbit

  $ tellmeabout() {
  > if [ -h $1 ]; then
  >     echo $1 is a symlink:
  >     $TESTDIR/readlink.py $1
  > elif [ -x $1 ]; then
  >     echo $1 is an executable file with content:
  >     cat $1
  > else
  >     echo $1 is a plain file with content:
  >     cat $1
  > fi
  > }

  $ hg init test1
  $ cd test1

  $ echo a > a
  $ hg ci -Aqmadd
  $ chmod +x a
  $ hg ci -mexecutable

  $ hg up -q 0
  $ rm a
  $ ln -s symlink a
  $ hg ci -msymlink
  created new head

Symlink is local parent, executable is other:

  $ hg merge --debug
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: c334dc3be0da, local: 521a1e40188f+, remote: 3574f3e69b1c
   preserving a for resolve of a
   a: versions differ -> m
  tool internal:merge (for pattern a) can't handle symlinks
  couldn't find merge tool hgmerge
  no tool found to merge a
  picked tool ':prompt' for a (binary False symlink True changedelete False)
  file 'a' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  0 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]

  $ tellmeabout a
  a is a symlink:
  a -> symlink
  $ hg resolve a --tool internal:other
  (no more unresolved files)
  $ tellmeabout a
  a is an executable file with content:
  a
  $ hg st
  M a
  ? a.orig

Symlink is other parent, executable is local:

  $ hg update -C 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg merge --debug --tool :union
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: c334dc3be0da, local: 3574f3e69b1c+, remote: 521a1e40188f
   preserving a for resolve of a
   a: versions differ -> m
  picked tool ':union' for a (binary False symlink True changedelete False)
  merging a
  my a@3574f3e69b1c+ other a@521a1e40188f ancestor a@c334dc3be0da
  warning: internal :union cannot merge symlinks for a
  warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
  0 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]

  $ tellmeabout a
  a is an executable file with content:
  a

  $ hg update -C 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg merge --debug --tool :merge3
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: c334dc3be0da, local: 3574f3e69b1c+, remote: 521a1e40188f
   preserving a for resolve of a
   a: versions differ -> m
  picked tool ':merge3' for a (binary False symlink True changedelete False)
  merging a
  my a@3574f3e69b1c+ other a@521a1e40188f ancestor a@c334dc3be0da
  warning: internal :merge3 cannot merge symlinks for a
  warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
  0 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]

  $ tellmeabout a
  a is an executable file with content:
  a

  $ hg update -C 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg merge --debug --tool :merge-local
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: c334dc3be0da, local: 3574f3e69b1c+, remote: 521a1e40188f
   preserving a for resolve of a
   a: versions differ -> m
  picked tool ':merge-local' for a (binary False symlink True changedelete False)
  merging a
  my a@3574f3e69b1c+ other a@521a1e40188f ancestor a@c334dc3be0da
  warning: internal :merge-local cannot merge symlinks for a
  0 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]

  $ tellmeabout a
  a is an executable file with content:
  a

  $ hg update -C 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg merge --debug --tool :merge-other
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: c334dc3be0da, local: 3574f3e69b1c+, remote: 521a1e40188f
   preserving a for resolve of a
   a: versions differ -> m
  picked tool ':merge-other' for a (binary False symlink True changedelete False)
  merging a
  my a@3574f3e69b1c+ other a@521a1e40188f ancestor a@c334dc3be0da
  warning: internal :merge-other cannot merge symlinks for a
  0 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]

  $ tellmeabout a
  a is an executable file with content:
  a

Update to link without local change should get us a symlink (issue3316):

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg up
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  updated to "521a1e40188f: symlink"
  1 other heads for branch "default"
  $ hg st
  ? a.orig

Update to link with local change should cause a merge prompt (issue3200):

  $ hg up -Cq 0
  $ echo data > a
  $ HGMERGE= hg up -y --debug --config ui.merge=
  resolving manifests
   branchmerge: False, force: False, partial: False
   ancestor: c334dc3be0da, local: c334dc3be0da+, remote: 521a1e40188f
   preserving a for resolve of a
   a: versions differ -> m
  (couldn't find merge tool hgmerge|tool hgmerge can't handle symlinks) (re)
  no tool found to merge a
  picked tool ':prompt' for a (binary False symlink True changedelete False)
  file 'a' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [destination], or leave (u)nresolved.
  What do you want to do? u
  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  updated to "521a1e40188f: symlink"
  1 other heads for branch "default"
  [1]
  $ hg diff --git
  diff --git a/a b/a
  old mode 120000
  new mode 100644
  --- a/a
  +++ b/a
  @@ -1,1 +1,1 @@
  -symlink
  \ No newline at end of file
  +data


Test only 'l' change - happens rarely, except when recovering from situations
where that was what happened.

  $ hg init test2
  $ cd test2
  $ printf base > f
  $ hg ci -Aqm0
  $ echo file > f
  $ echo content >> f
  $ hg ci -qm1
  $ hg up -qr0
  $ rm f
  $ ln -s base f
  $ hg ci -qm2
  $ hg merge
  tool internal:merge (for pattern f) can't handle symlinks
  no tool found to merge f
  file 'f' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  0 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]
  $ tellmeabout f
  f is a symlink:
  f -> base

  $ hg up -Cqr1
  $ hg merge
  tool internal:merge (for pattern f) can't handle symlinks
  no tool found to merge f
  file 'f' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  0 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]
  $ tellmeabout f
  f is a plain file with content:
  file
  content

  $ cd ..

Test removed 'x' flag merged with change to symlink

  $ hg init test3
  $ cd test3
  $ echo f > f
  $ chmod +x f
  $ hg ci -Aqm0
  $ chmod -x f
  $ hg ci -qm1
  $ hg up -qr0
  $ rm f
  $ ln -s dangling f
  $ hg ci -qm2
  $ hg merge
  tool internal:merge (for pattern f) can't handle symlinks
  no tool found to merge f
  file 'f' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  0 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]
  $ tellmeabout f
  f is a symlink:
  f -> dangling

  $ hg up -Cqr1
  $ hg merge
  tool internal:merge (for pattern f) can't handle symlinks
  no tool found to merge f
  file 'f' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  0 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]
  $ tellmeabout f
  f is a plain file with content:
  f

Test removed 'x' flag merged with content change - both ways

  $ hg up -Cqr0
  $ echo change > f
  $ hg ci -qm3
  $ hg merge -r1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ tellmeabout f
  f is a plain file with content:
  change

  $ hg up -qCr1
  $ hg merge -r3
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ tellmeabout f
  f is a plain file with content:
  change

  $ cd ..

Test merge with no common ancestor:
a: just different
b: x vs -, different (cannot calculate x, cannot ask merge tool)
c: x vs -, same (cannot calculate x, merge tool is no good)
d: x vs l, different
e: x vs l, same
f: - vs l, different
g: - vs l, same
h: l vs l, different
(where same means the filelog entry is shared and there thus is an ancestor!)

  $ hg init test4
  $ cd test4
  $ echo 0 > 0
  $ hg ci -Aqm0

  $ echo 1 > a
  $ echo 1 > b
  $ chmod +x b
  $ echo 1 > bx
  $ chmod +x bx
  $ echo x > c
  $ chmod +x c
  $ echo 1 > d
  $ chmod +x d
  $ printf x > e
  $ chmod +x e
  $ echo 1 > f
  $ printf x > g
  $ ln -s 1 h
  $ hg ci -qAm1

  $ hg up -qr0
  $ echo 2 > a
  $ echo 2 > b
  $ echo 2 > bx
  $ chmod +x bx
  $ echo x > c
  $ ln -s 2 d
  $ ln -s x e
  $ ln -s 2 f
  $ ln -s x g
  $ ln -s 2 h
  $ hg ci -Aqm2

  $ hg merge
  merging a
  warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
  warning: cannot merge flags for b without common ancestor - keeping local flags
  merging b
  warning: conflicts while merging b! (edit, then use 'hg resolve --mark')
  merging bx
  warning: conflicts while merging bx! (edit, then use 'hg resolve --mark')
  warning: cannot merge flags for c without common ancestor - keeping local flags
  tool internal:merge (for pattern d) can't handle symlinks
  no tool found to merge d
  file 'd' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  tool internal:merge (for pattern f) can't handle symlinks
  no tool found to merge f
  file 'f' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  tool internal:merge (for pattern h) can't handle symlinks
  no tool found to merge h
  file 'h' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  3 files updated, 0 files merged, 0 files removed, 6 files unresolved
  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
  [1]
  $ hg resolve -l
  U a
  U b
  U bx
  U d
  U f
  U h
  $ tellmeabout a
  a is a plain file with content:
  <<<<<<< working copy: 0c617753b41b - test: 2
  2
  =======
  1
  >>>>>>> merge rev:    2e60aa20b912 - test: 1
  $ tellmeabout b
  b is a plain file with content:
  <<<<<<< working copy: 0c617753b41b - test: 2
  2
  =======
  1
  >>>>>>> merge rev:    2e60aa20b912 - test: 1
  $ tellmeabout c
  c is a plain file with content:
  x
  $ tellmeabout d
  d is a symlink:
  d -> 2
  $ tellmeabout e
  e is a symlink:
  e -> x
  $ tellmeabout f
  f is a symlink:
  f -> 2
  $ tellmeabout g
  g is a symlink:
  g -> x
  $ tellmeabout h
  h is a symlink:
  h -> 2

  $ hg up -Cqr1
  $ hg merge
  merging a
  warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
  warning: cannot merge flags for b without common ancestor - keeping local flags
  merging b
  warning: conflicts while merging b! (edit, then use 'hg resolve --mark')
  merging bx
  warning: conflicts while merging bx! (edit, then use 'hg resolve --mark')
  warning: cannot merge flags for c without common ancestor - keeping local flags
  tool internal:merge (for pattern d) can't handle symlinks
  no tool found to merge d
  file 'd' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  tool internal:merge (for pattern f) can't handle symlinks
  no tool found to merge f
  file 'f' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  tool internal:merge (for pattern h) can't handle symlinks
  no tool found to merge h
  file 'h' needs to be resolved.
  You can keep (l)ocal [working copy], take (o)ther [merge rev], or leave (u)nresolved.
  What do you want to do? u
  3 files updated, 0 files merged, 0 files removed, 6 files unresolved
  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
  [1]
  $ tellmeabout a
  a is a plain file with content:
  <<<<<<< working copy: 2e60aa20b912 - test: 1
  1
  =======
  2
  >>>>>>> merge rev:    0c617753b41b - test: 2
  $ tellmeabout b
  b is an executable file with content:
  <<<<<<< working copy: 2e60aa20b912 - test: 1
  1
  =======
  2
  >>>>>>> merge rev:    0c617753b41b - test: 2
  $ tellmeabout c
  c is an executable file with content:
  x
  $ tellmeabout d
  d is an executable file with content:
  1
  $ tellmeabout e
  e is an executable file with content:
  x (no-eol)
  $ tellmeabout f
  f is a plain file with content:
  1
  $ tellmeabout g
  g is a plain file with content:
  x (no-eol)
  $ tellmeabout h
  h is a symlink:
  h -> 1

  $ cd ..