tests/test-diff-change.t

interfaces: add the optional `bdiff.xdiffblocks()` method

PyCharm flagged where this was called on the protocol class in `mdiff.py` in the
previous commit, but pytype completely missed it.  PyCharm is correct here, but
I'm committing this separately to highlight this potential problem- some of the
implementations don't implement _all_ of the methods the others do, and there's
not a great way to indicate on a protocol class that a method or attribute is
optional- that's kinda the opposite of what static typing is about.

Making the method an `Optional[Callable]` attribute works here, and keeps both
PyCharm and pytype happy, and the generated `mdiff.pyi` and `modules.pyi` look
reasonable.  We might be getting a little lucky, because the method isn't
invoked directly- it is returned from another method that selects which block
function to use.  Except since it is declared on the protocol class, every
module needs this attribute (in theory, but in practice this doesn't seem to be
checked), so the check for it on the module has to change from `hasattr()` to
`getattr(..., None)`.  We defer defining the optional attrs to the type checking
phase as an extra precaution- that way it isn't an attr with a `None` value at
runtime if someone is still using `hasattr()`.

As to why pytype missed this, I have no clue.  The generated `mdiff.pyi` even
has the global variable typed as `bdiff: intmod.BDiff`, so uses of it really
should comply with what is on the class, protocol class or not.

Testing diff --change, --from, --to

  $ hg init a
  $ cd a

  $ echo "first" > file.txt
  $ hg add file.txt
  $ hg commit -m 'first commit' # 0

  $ echo "second" > file.txt
  $ hg commit -m 'second commit' # 1

  $ echo "third" > file.txt
  $ hg commit -m 'third commit' # 2

  $ hg diff --nodates --change 1
  diff -r 4bb65dda5db4 -r e9b286083166 file.txt
  --- a/file.txt
  +++ b/file.txt
  @@ -1,1 +1,1 @@
  -first
  +second

  $ hg diff --change e9b286083166
  diff -r 4bb65dda5db4 -r e9b286083166 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -first
  +second

Test --from and --to

  $ hg diff --from . --rev .
  abort: cannot specify both --from and --rev
  [10]
  $ hg diff --to . --rev .
  abort: cannot specify both --to and --rev
  [10]
  $ hg diff --from . --change .
  abort: cannot specify both --from and --change
  [10]
  $ hg diff --to . --change .
  abort: cannot specify both --to and --change
  [10]
  $ echo dirty > file.txt
  $ hg diff --from .
  diff -r bf5ff72eb7e0 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -third
  +dirty
  $ hg diff --from . --reverse
  diff -r bf5ff72eb7e0 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -dirty
  +third
  $ hg diff --to .
  diff -r bf5ff72eb7e0 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -dirty
  +third
  $ hg diff --from 0 --to 2
  diff -r 4bb65dda5db4 -r bf5ff72eb7e0 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -first
  +third
  $ hg diff --from 2 --to 0
  diff -r bf5ff72eb7e0 -r 4bb65dda5db4 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -third
  +first
  $ hg co -C .
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd ..

Test dumb revspecs: top-level "x:y", "x:", ":y" and ":" ranges should be handled
as pairs even if x == y, but not for "f(x:y)" nor "x::y" (issue3474, issue4774)

  $ hg clone -q a dumbspec
  $ cd dumbspec
  $ echo "wdir" > file.txt

  $ hg diff -r 2:2
  $ hg diff -r 2:.
  $ hg diff -r 2:
  $ hg diff -r :0
  $ hg diff -r '2:first(2:2)'
  $ hg diff -r 'first(2:2)' --nodates
  diff -r bf5ff72eb7e0 file.txt
  --- a/file.txt
  +++ b/file.txt
  @@ -1,1 +1,1 @@
  -third
  +wdir
  $ hg diff -r '(2:2)' --nodates
  diff -r bf5ff72eb7e0 file.txt
  --- a/file.txt
  +++ b/file.txt
  @@ -1,1 +1,1 @@
  -third
  +wdir
  $ hg diff -r 2::2 --nodates
  diff -r bf5ff72eb7e0 file.txt
  --- a/file.txt
  +++ b/file.txt
  @@ -1,1 +1,1 @@
  -third
  +wdir
  $ hg diff -r "2 and 1"
  abort: empty revision range
  [10]

  $ cd ..

  $ hg clone -qr0 a dumbspec-rev0
  $ cd dumbspec-rev0
  $ echo "wdir" > file.txt

  $ hg diff -r :
  $ hg diff -r 'first(:)' --nodates
  diff -r 4bb65dda5db4 file.txt
  --- a/file.txt
  +++ b/file.txt
  @@ -1,1 +1,1 @@
  -first
  +wdir

  $ cd ..

Testing diff --change when merge:

  $ cd a

  $ for i in 1 2 3 4 5 6 7 8 9 10; do
  >    echo $i >> file.txt
  > done
  $ hg commit -m "lots of text" # 3

  $ sed -e 's,^2$,x,' file.txt > file.txt.tmp
  $ mv file.txt.tmp file.txt
  $ hg commit -m "change 2 to x" # 4

  $ hg up -r 3
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ sed -e 's,^8$,y,' file.txt > file.txt.tmp
  $ mv file.txt.tmp file.txt
  $ hg commit -m "change 8 to y"
  created new head

  $ hg up -C -r 4
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg merge -r 5
  merging file.txt
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -m "merge 8 to y" # 6

  $ hg diff --change 5
  diff -r ae119d680c82 -r 9085c5c02e52 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -6,6 +6,6 @@
   5
   6
   7
  -8
  +y
   9
   10

must be similar to 'hg diff --change 5':

  $ hg diff -c 6
  diff -r 273b50f17c6d -r 979ca961fd2e file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -6,6 +6,6 @@
   5
   6
   7
  -8
  +y
   9
   10

merge diff should show only manual edits to a merge:

  $ hg diff --config diff.merge=yes -c 6
(no diff output is expected here)

Construct an "evil merge" that does something other than just the merge.

  $ hg co ".^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg merge -r 5
  merging file.txt
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ echo 11 >> file.txt
  $ hg ci -m 'merge 8 to y with manual edit of 11' # 7
  created new head
  $ hg diff -c 7
  diff -r 273b50f17c6d -r 8ad85e839ba7 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -6,6 +6,7 @@
   5
   6
   7
  -8
  +y
   9
   10
  +11
Contrast with the `hg diff -c 7` version above: only the manual edit shows
up, making it easy to identify changes someone is otherwise trying to sneak
into a merge.
  $ hg diff --config diff.merge=yes -c 7
  diff -r 8ad85e839ba7 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -9,3 +9,4 @@
   y
   9
   10
  +11

Set up a conflict.
  $ hg co ".^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ sed -e 's,^8$,z,' file.txt > file.txt.tmp
  $ mv file.txt.tmp file.txt
  $ hg ci -m 'conflicting edit: 8 to z'
  created new head
  $ echo "this file is new in p1 of the merge" > new-file-p1.txt
  $ hg ci -Am 'new file' new-file-p1.txt
  $ hg log -r . --template 'p1 will be rev {rev}\n'
  p1 will be rev 9
  $ hg co 5
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo "this file is new in p2 of the merge" > new-file-p2.txt
  $ hg ci -Am 'new file' new-file-p2.txt
  created new head
  $ hg log -r . --template 'p2 will be rev {rev}\n'
  p2 will be rev 10
  $ hg co -- 9
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg merge -r 10
  merging file.txt
  warning: conflicts while merging file.txt! (edit, then use 'hg resolve --mark')
  1 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 revert file.txt -r .
  $ hg resolve -ma
  (no more unresolved files)
  $ hg commit -m 'merge conflicted edit'
Without diff.merge, it's a diff against p1
  $ hg diff --config diff.merge=no -c 11
  diff -r fd1f17c90d7c -r 5010caab09f6 new-file-p2.txt
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/new-file-p2.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,1 @@
  +this file is new in p2 of the merge
With diff.merge, it's a diff against the conflicted content.
  $ hg diff --config diff.merge=yes -c 11
  diff -r 5010caab09f6 file.txt
  --- a/file.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/file.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -6,12 +6,6 @@
   5
   6
   7
  -<<<<<<< local: fd1f17c90d7c - test: new file
   z
  -||||||| base:  ae119d680c82 - test: lots of text
  -8
  -=======
  -y
  ->>>>>>> other: d9e7de69eac3 - test: new file
   9
   10

There must _NOT_ be a .hg/merge directory leftover.
  $ test ! -d .hg/merge
(No output is expected)
  $ cd ..