copies: calculate mergecopies() based on pathcopies()
When copies are stored in changesets, we need a changeset-centric
version of mergecopies() just like we have a changeset-centric version
of pathcopies(). I think the natural way of thinking about
mergecopies() is in terms of pathcopies() from the base to each of the
commits. So if we can rewrite mergecopies() based on two such
pathcopies() calls, we'll get the changeset-centric version for
free. That's what this patch does.
A nice bonus is that it ends up being a lot simpler. mergecopies() has
accumulated a lot of technical debt over time. One good example is the
code for dealing with grafts (the "partial/incomplete/dirty"
stuff). Since pathcopies() already deals with backwards renames and
ping-pong renames, we get that for free.
I've run tests with hard-coded debug logging for "fullcopy" and while
I haven't looked at every difference it produces, all the ones I have
looked at seemed reasonable to me. I'm a little surprised that no more
tests fail when run with '--extra-config-opt
experimental.copies.read-from=compatibility' compared to before this
patch. This patch also fixes the broken cases in test-annotate.t and
test-fastannotate.t. It also enables the part of test-copies.t that
was previously disabled exactly because mergecopies() needed to get a
changeset-centric version.
One drawback of the rewritten code is that we may now make
remotefilelog prefetch more files. We used to prefetch files that were
unique to either side of the merge compared to the other. We now
prefetch files that are unique to either side of the merge compared to
the base. This means that if you added the same file to each side, we
would not prefetch it before, but we would now. Such cases are
probably quite rare, but one likely scenario where they happen is when
moving from a commit to its successor (or the other way around). The
user will probably already have the files in the cache in such cases,
so it's probably not a big deal.
Some timings for calculating mergecopies between two revisions
(revisions shown on each line, all using the common ancestor as base):
In the hg repo:
4.8 4.9: 0.21s -> 0.21s
4.0 4.8: 0.35s -> 0.63s
In and old copy of the mozilla-unified repo:
FIREFOX_BETA_60_BASE^ FIREFOX_BETA_60_BASE: 0.82s -> 0.82s
FIREFOX_NIGHTLY_59_END FIREFOX_BETA_60_BASE: 2.5s -> 2.6s
FIREFOX_BETA_59_END FIREFOX_BETA_60_BASE: 3.9s -> 4.1s
FIREFOX_AURORA_50_BASE FIREFOX_BETA_60_BASE: 31s -> 33s
So it's measurably slower in most cases. The most significant
difference is in the hg repo between revisions 4.0 and 4.8. In that
case it seems to come from the fact that pathcopies() uses
fctx.isintroducedafter() (in _tracefile), while the old mergecopies()
used fctx.linkrev() (in _checkcopies()). That results in a single call
to filectx._adjustlinkrev(), which is responsible for the entire
difference in time (in my repo). So we pay a performance penalty but
we get more correct code (see change in
test-mv-cp-st-diff.t). Deleting the "== f.filenode()" in _tracefile()
recovers the lost performance in the hg repo.
There were are few other optimizations in _checkcopies() that I could
not measure any impact from. One was from the "seen" set. Another was
from a "continue" when the file was not in the destination manifest
(corresponding to "am" in _tracefile).
Also note that merge copies are not calculated when updating with a
clean working copy, which is probably the most common case. I
therefore think the much simpler code is worth the slowdown.
Differential Revision: https://phab.mercurial-scm.org/D6255
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ tipparents() {
> hg parents --template "{rev}:{node|short} {desc|firstline}\n" -r tip
> }
Test import and merge diffs
$ hg init repo
$ cd repo
$ echo a > a
$ hg ci -Am adda
adding a
$ echo a >> a
$ hg ci -m changea
$ echo c > c
$ hg ci -Am addc
adding c
$ hg up 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo b > b
$ hg ci -Am addb
adding b
created new head
$ hg up 1
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg merge 3
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -m merge
$ hg export . > ../merge.diff
$ grep -v '^merge$' ../merge.diff > ../merge.nomsg.diff
$ cd ..
$ hg clone -r2 repo repo2
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 2 files
new changesets 07f494440405:890ecaa90481
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd repo2
$ hg pull -r3 ../repo
pulling from ../repo
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 102a90ea7b4a
(run 'hg heads' to see heads, 'hg merge' to merge)
Test without --exact and diff.p1 == workingdir.p1
$ hg up 1
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat > $TESTTMP/editor.sh <<EOF
> env | grep HGEDITFORM
> echo merge > \$1
> EOF
$ HGEDITOR="sh $TESTTMP/editor.sh" hg import --edit ../merge.nomsg.diff
applying ../merge.nomsg.diff
HGEDITFORM=import.normal.merge
$ tipparents
1:540395c44225 changea
3:102a90ea7b4a addb
$ hg strip --no-backup tip
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
Test without --exact and diff.p1 != workingdir.p1
$ hg up 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg import ../merge.diff
applying ../merge.diff
warning: import the patch as a normal revision
(use --exact to import the patch as a merge)
$ tipparents
2:890ecaa90481 addc
$ hg strip --no-backup tip
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
Test with --exact
$ hg import --exact ../merge.diff
applying ../merge.diff
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ tipparents
1:540395c44225 changea
3:102a90ea7b4a addb
$ hg strip --no-backup tip
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
Test with --bypass and diff.p1 == workingdir.p1
$ hg up 1
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg import --bypass ../merge.diff
applying ../merge.diff
$ tipparents
1:540395c44225 changea
3:102a90ea7b4a addb
$ hg strip --no-backup tip
Test with --bypass and diff.p1 != workingdir.p1
$ hg up 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg import --bypass ../merge.diff
applying ../merge.diff
warning: import the patch as a normal revision
(use --exact to import the patch as a merge)
$ tipparents
2:890ecaa90481 addc
$ hg strip --no-backup tip
Test with --bypass and --exact
$ hg import --bypass --exact ../merge.diff
applying ../merge.diff
$ tipparents
1:540395c44225 changea
3:102a90ea7b4a addb
$ hg strip --no-backup tip
$ cd ..
Test that --exact on a bad header doesn't corrupt the repo (issue3616)
$ hg init repo3
$ cd repo3
$ echo a>a
$ hg ci -Aqm0
$ echo a>>a
$ hg ci -m1
$ echo a>>a
$ hg ci -m2
$ echo a>a
$ echo b>>a
$ echo a>>a
$ hg ci -m3
$ hg export 2 | head -7 > ../a.patch
$ hg export tip > out
>>> apatch = open("../a.patch", "ab")
>>> apatch.write(b"".join(open("out", 'rb').readlines()[7:])) and None
$ cd ..
$ hg clone -qr0 repo3 repo3-clone
$ cd repo3-clone
$ hg pull -qr1 ../repo3
$ hg import --exact ../a.patch
applying ../a.patch
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
patching file a
Hunk #1 succeeded at 1 with fuzz 1 (offset -1 lines).
transaction abort!
rollback completed
abort: patch is damaged or loses information
[255]
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
checked 2 changesets with 2 changes to 1 files