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.
# init
$ hg init
$ echo a > a
$ hg add a
$ hg commit -m'a'
$ echo b > b
$ hg add b
$ hg commit -m'b'
$ hg up -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo c > c
$ hg add c
$ hg commit -m'c'
created new head
# test merging of diverged bookmarks
$ hg bookmark -r 1 "c@diverge"
$ hg bookmark -r 1 b
$ hg bookmark c
$ hg bookmarks
b 1:d2ae7f538514
* c 2:d36c0562f908
c@diverge 1:d2ae7f538514
$ hg merge "c@diverge"
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg commit -m'merge'
$ hg bookmarks
b 1:d2ae7f538514
* c 3:b8f96cf4688b
$ hg up -C 3
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(leaving bookmark c)
$ echo d > d
$ hg add d
$ hg commit -m'd'
$ hg up -C 3
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo e > e
$ hg add e
$ hg commit -m'e'
created new head
$ hg up -C 5
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg bookmark e
$ hg bookmarks
b 1:d2ae7f538514
c 3:b8f96cf4688b
* e 5:26bee9c5bcf3
# the picked side is bookmarked
$ hg up -C 4
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(leaving bookmark e)
$ hg merge
abort: heads are bookmarked - please merge with an explicit rev
(run 'hg heads' to see all heads)
[255]
# our revision is bookmarked
$ hg up -C e
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(activating bookmark e)
$ hg merge
abort: no matching bookmark to merge - please merge with an explicit rev or bookmark
(run 'hg heads' to see all heads)
[255]
# merge bookmark heads
$ hg up -C 4
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(leaving bookmark e)
$ echo f > f
$ hg commit -Am "f"
adding f
$ hg bookmarks -r 4 "e@diverged"
$ hg up -q -C "e@diverged"
$ hg merge
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg parents
changeset: 4:a0546fcfe0fb
bookmark: e@diverged
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: d
changeset: 5:26bee9c5bcf3
bookmark: e
parent: 3:b8f96cf4688b
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: e
$ hg up -C e
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(activating bookmark e)
$ hg bookmarks
b 1:d2ae7f538514
c 3:b8f96cf4688b
* e 5:26bee9c5bcf3
e@diverged 4:a0546fcfe0fb
$ hg merge
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg commit -m'merge'
$ hg bookmarks
b 1:d2ae7f538514
c 3:b8f96cf4688b
* e 7:ca784329f0ba
# test warning when all heads are inactive bookmarks
$ hg up -C 6
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(leaving bookmark e)
$ echo g > g
$ hg commit -Am 'g'
adding g
$ hg bookmark -i g
$ hg bookmarks
b 1:d2ae7f538514
c 3:b8f96cf4688b
e 7:ca784329f0ba
g 8:04dd21731d95
$ hg heads
changeset: 8:04dd21731d95
bookmark: g
tag: tip
parent: 6:be381d1126a0
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: g
changeset: 7:ca784329f0ba
bookmark: e
parent: 5:26bee9c5bcf3
parent: 4:a0546fcfe0fb
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: merge
$ hg merge
abort: heads are bookmarked - please merge with an explicit rev
(run 'hg heads' to see all heads)
[255]