merge: minimize conflicts when common base is not shown (
issue4447)
Previously, two changes that were nearly, but not quite, identical would result
in large merge conflict regions that looked very similar, and were thus very
confusing to users, and lead people used to other source control systems to
claim that "mercurial's merge algorithms suck". In the relatively common case
of a new file being introduced in two branches with very slight modifications,
the old behavior would show the entire file as a conflict, and it would be very
difficult for a user to determine what was going on.
In the past, mercurial attempted to solve this with a "very smart" algorithm
that would find all common lines, but this has significant problems as
described in
2ea6d906cf9b.
Instead, we use a "very dumb" algorithm introduced in the previous patch that
simply matches lines at the periphery of conflict regions. This minimizes most
conflict regions well, though there may still be some degenerate edge cases,
like small modification to the beginning and end of a large file.
$ hg init t
$ cd t
$ cat > unix2dos.py <<EOF
> import sys
>
> for path in sys.argv[1:]:
> data = file(path, 'rb').read()
> data = data.replace('\n', '\r\n')
> file(path, 'wb').write(data)
> EOF
$ echo '[hooks]' >> .hg/hgrc
$ echo 'pretxncommit.crlf = python:hgext.win32text.forbidcrlf' >> .hg/hgrc
$ echo 'pretxnchangegroup.crlf = python:hgext.win32text.forbidcrlf' >> .hg/hgrc
$ cat .hg/hgrc
[hooks]
pretxncommit.crlf = python:hgext.win32text.forbidcrlf
pretxnchangegroup.crlf = python:hgext.win32text.forbidcrlf
$ echo hello > f
$ hg add f
commit should succeed
$ hg ci -m 1
$ hg clone . ../zoz
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cp .hg/hgrc ../zoz/.hg
$ python unix2dos.py f
commit should fail
$ hg ci -m 2.1
attempt to commit or push text file(s) using CRLF line endings
in f583ea08d42a: f
transaction abort!
rollback completed
abort: pretxncommit.crlf hook failed
[255]
$ mv .hg/hgrc .hg/hgrc.bak
commits should succeed
$ hg ci -m 2
$ hg cp f g
$ hg ci -m 2.2
push should fail
$ hg push ../zoz
pushing to ../zoz
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 2 files
attempt to commit or push text file(s) using CRLF line endings
in bc2d09796734: g
in b1aa5cde7ff4: f
To prevent this mistake in your local repository,
add to Mercurial.ini or .hg/hgrc:
[hooks]
pretxncommit.crlf = python:hgext.win32text.forbidcrlf
and also consider adding:
[extensions]
win32text =
[encode]
** = cleverencode:
[decode]
** = cleverdecode:
transaction abort!
rollback completed
abort: pretxnchangegroup.crlf hook failed
[255]
$ mv .hg/hgrc.bak .hg/hgrc
$ echo hello > f
$ hg rm g
commit should succeed
$ hg ci -m 2.3
push should succeed
$ hg push ../zoz
pushing to ../zoz
searching for changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 2 files
and now for something completely different
$ mkdir d
$ echo hello > d/f2
$ python unix2dos.py d/f2
$ hg add d/f2
$ hg ci -m 3
attempt to commit or push text file(s) using CRLF line endings
in 053ba1a3035a: d/f2
transaction abort!
rollback completed
abort: pretxncommit.crlf hook failed
[255]
$ hg revert -a
forgetting d/f2 (glob)
$ rm d/f2
$ hg rem f
$ hg ci -m 4
$ $PYTHON -c 'file("bin", "wb").write("hello\x00\x0D\x0A")'
$ hg add bin
$ hg ci -m 5
$ hg log -v
changeset: 5:f0b1c8d75fce
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: bin
description:
5
changeset: 4:77796dbcd4ad
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f
description:
4
changeset: 3:7c1b5430b350
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f g
description:
2.3
changeset: 2:bc2d09796734
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: g
description:
2.2
changeset: 1:b1aa5cde7ff4
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f
description:
2
changeset: 0:fcf06d5c4e1d
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f
description:
1
$ hg clone . dupe
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ for x in a b c d; do echo content > dupe/$x; done
$ hg -R dupe add
adding dupe/a (glob)
adding dupe/b (glob)
adding dupe/c (glob)
adding dupe/d (glob)
$ python unix2dos.py dupe/b dupe/c dupe/d
$ hg -R dupe ci -m a dupe/a
$ hg -R dupe ci -m b/c dupe/[bc]
$ hg -R dupe ci -m d dupe/d
$ hg -R dupe log -v
changeset: 8:67ac5962ab43
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: d
description:
d
changeset: 7:68c127d1834e
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: b c
description:
b/c
changeset: 6:adbf8bf7f31d
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: a
description:
a
changeset: 5:f0b1c8d75fce
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: bin
description:
5
changeset: 4:77796dbcd4ad
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f
description:
4
changeset: 3:7c1b5430b350
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f g
description:
2.3
changeset: 2:bc2d09796734
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: g
description:
2.2
changeset: 1:b1aa5cde7ff4
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f
description:
2
changeset: 0:fcf06d5c4e1d
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f
description:
1
$ hg pull dupe
pulling from dupe
searching for changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 4 changes to 4 files
attempt to commit or push text file(s) using CRLF line endings
in 67ac5962ab43: d
in 68c127d1834e: b
in 68c127d1834e: c
To prevent this mistake in your local repository,
add to Mercurial.ini or .hg/hgrc:
[hooks]
pretxncommit.crlf = python:hgext.win32text.forbidcrlf
and also consider adding:
[extensions]
win32text =
[encode]
** = cleverencode:
[decode]
** = cleverdecode:
transaction abort!
rollback completed
abort: pretxnchangegroup.crlf hook failed
[255]
$ hg log -v
changeset: 5:f0b1c8d75fce
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: bin
description:
5
changeset: 4:77796dbcd4ad
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f
description:
4
changeset: 3:7c1b5430b350
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f g
description:
2.3
changeset: 2:bc2d09796734
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: g
description:
2.2
changeset: 1:b1aa5cde7ff4
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f
description:
2
changeset: 0:fcf06d5c4e1d
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files: f
description:
1
$ rm .hg/hgrc
$ (echo some; echo text) > f3
$ $PYTHON -c 'file("f4.bat", "wb").write("rem empty\x0D\x0A")'
$ hg add f3 f4.bat
$ hg ci -m 6
$ cat bin
hello\x00\r (esc)
$ cat f3
some
text
$ cat f4.bat
rem empty\r (esc)
$ echo '[extensions]' >> .hg/hgrc
$ echo 'win32text = ' >> .hg/hgrc
$ echo '[decode]' >> .hg/hgrc
$ echo '** = cleverdecode:' >> .hg/hgrc
$ echo '[encode]' >> .hg/hgrc
$ echo '** = cleverencode:' >> .hg/hgrc
$ cat .hg/hgrc
[extensions]
win32text =
[decode]
** = cleverdecode:
[encode]
** = cleverencode:
Trigger deprecation warning:
$ hg id -t
win32text is deprecated: https://mercurial-scm.org/wiki/Win32TextExtension
tip
Disable warning:
$ echo '[win32text]' >> .hg/hgrc
$ echo 'warn = no' >> .hg/hgrc
$ hg id -t
tip
$ rm f3 f4.bat bin
$ hg co -C
WARNING: f4.bat already has CRLF line endings
and does not need EOL conversion by the win32text plugin.
Before your next commit, please reconsider your encode/decode settings in
Mercurial.ini or $TESTTMP/t/.hg/hgrc. (glob)
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat bin
hello\x00\r (esc)
$ cat f3
some\r (esc)
text\r (esc)
$ cat f4.bat
rem empty\r (esc)
$ $PYTHON -c 'file("f5.sh", "wb").write("# empty\x0D\x0A")'
$ hg add f5.sh
$ hg ci -m 7
$ cat f5.sh
# empty\r (esc)
$ hg cat f5.sh
# empty
$ echo '% just linefeed' > linefeed
$ hg ci -qAm 8 linefeed
$ cat linefeed
% just linefeed
$ hg cat linefeed
% just linefeed
$ hg st -q
$ hg revert -a linefeed
no changes needed to linefeed
$ cat linefeed
% just linefeed
$ hg st -q
$ echo modified >> linefeed
$ hg st -q
M linefeed
$ hg revert -a
reverting linefeed
$ hg st -q
$ cat linefeed
% just linefeed\r (esc)
$ cd ..