absorb: preserve changesets which were already empty
Most commands in Mercurial (commit, rebase, absorb itself) don’t create empty
changesets or drop them if they become empty. If there’s a changeset that’s
empty, it must be a deliberate choice of the user. At least it shouldn’t be
absorb’s responsibility to prune them. The fact that changesets that became
empty during absorb are pruned, is unaffected by this.
This case was found while writing patches which make it possible to configure
absorb and rebase to not drop empty changesets. Even without having such config
set, I think it’s valuable to preserve changesets which were already empty.
# reproduce issue2264, issue2516
create test repo
$ cat <<EOF >> $HGRCPATH
> [extensions]
> transplant =
> EOF
$ hg init repo
$ cd repo
$ template="{rev} {desc|firstline} [{branch}]\n"
# we need to start out with two changesets on the default branch
# in order to avoid the cute little optimization where transplant
# pulls rather than transplants
add initial changesets
$ echo feature1 > file1
$ hg ci -Am"feature 1"
adding file1
$ echo feature2 >> file2
$ hg ci -Am"feature 2"
adding file2
# The changes to 'bugfix' are enough to show the bug: in fact, with only
# those changes, it's a very noisy crash ("RuntimeError: nothing
# committed after transplant"). But if we modify a second file in the
# transplanted changesets, the bug is much more subtle: transplant
# silently drops the second change to 'bugfix' on the floor, and we only
# see it when we run 'hg status' after transplanting. Subtle data loss
# bugs are worse than crashes, so reproduce the subtle case here.
commit bug fixes on bug fix branch
$ hg branch fixes
marked working directory as branch fixes
(branches are permanent and global, did you want a bookmark?)
$ echo fix1 > bugfix
$ echo fix1 >> file1
$ hg ci -Am"fix 1"
adding bugfix
$ echo fix2 > bugfix
$ echo fix2 >> file1
$ hg ci -Am"fix 2"
$ hg log -G --template="$template"
@ 3 fix 2 [fixes]
|
o 2 fix 1 [fixes]
|
o 1 feature 2 [default]
|
o 0 feature 1 [default]
transplant bug fixes onto release branch
$ hg update 0
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ hg branch release
marked working directory as branch release
$ hg transplant 2 3
applying [0-9a-f]{12} (re)
[0-9a-f]{12} transplanted to [0-9a-f]{12} (re)
applying [0-9a-f]{12} (re)
[0-9a-f]{12} transplanted to [0-9a-f]{12} (re)
$ hg log -G --template="$template"
@ 5 fix 2 [release]
|
o 4 fix 1 [release]
|
| o 3 fix 2 [fixes]
| |
| o 2 fix 1 [fixes]
| |
| o 1 feature 2 [default]
|/
o 0 feature 1 [default]
$ hg status
$ hg status --rev 0:4
M file1
A bugfix
$ hg status --rev 4:5
M bugfix
M file1
now test that we fixed the bug for all scripts/extensions
$ cat > $TESTTMP/committwice.py <<__EOF__
> import time
> from mercurial import hg, match, node, ui as uimod
>
> def replacebyte(fn, b):
> f = open(fn, "rb+")
> f.seek(0, 0)
> f.write(b)
> f.close()
>
> def printfiles(repo, rev):
> repo.ui.status(b"revision %d files: [%s]\n"
> % (rev, b', '.join(b"'%s'" % f
> for f in repo[rev].files())))
>
> repo = hg.repository(uimod.ui.load(), b'.')
> assert len(repo) == 6, "initial: len(repo): %d, expected: 6" % len(repo)
>
> replacebyte(b"bugfix", b"u")
> time.sleep(2)
> try:
> repo.ui.status(b"PRE: len(repo): %d\n" % len(repo))
> wlock = repo.wlock()
> lock = repo.lock()
> replacebyte(b"file1", b"x")
> repo.commit(text=b"x", user=b"test", date=(0, 0))
> replacebyte(b"file1", b"y")
> repo.commit(text=b"y", user=b"test", date=(0, 0))
> repo.ui.status(b"POST: len(repo): %d\n" % len(repo))
> finally:
> lock.release()
> wlock.release()
> printfiles(repo, 6)
> printfiles(repo, 7)
> __EOF__
$ "$PYTHON" $TESTTMP/committwice.py
PRE: len(repo): 6
POST: len(repo): 8
revision 6 files: ['bugfix', 'file1']
revision 7 files: ['file1']
Do a size-preserving modification outside of that process
$ echo abcd > bugfix
$ hg status
M bugfix
$ hg log --template "{rev} {desc} {files}\n" -r5:
5 fix 2 bugfix file1
6 x bugfix file1
7 y file1
$ cd ..