filectx.parents: enforce changeid of parent to be in own changectx ancestors
Because of the way filenodes are computed, you can have multiple changesets
"introducing" the same file revision. For example, in the changeset graph
below, changeset 2 and 3 both change a file -to- and -from- the same content.
o 3: content = new
|
| o 2: content = new
|/
o 1: content = old
In such cases, the file revision is create once, when 2 is added, and just reused
for 3. So the file change in '3' (from "old" to "new)" has no linkrev pointing
to it). We'll call this situation "linkrev-shadowing". As the linkrev is used for
optimization purposes when walking a file history, the linkrev-shadowing
results in an unexpected jump to another branch during such a walk.. This leads to
multiple bugs with log, annotate and rename detection.
One element to fix such bugs is to ensure that walking the file history sticks on
the same topology as the changeset's history. For this purpose, we extend the
logic in 'basefilectx.parents' so that it always defines the proper changeset
to associate the parent file revision with. This "proper" changeset has to be an
ancestor of the changeset associated with the child file revision.
This logic is performed in the '_adjustlinkrev' function. This function is
given the starting changeset and all the information regarding the parent file
revision. If the linkrev for the file revision is an ancestor of the starting
changeset, the linkrev is valid and will be used. If it is not, we detected a
topological jump caused by linkrev shadowing, we are going to walk the
ancestors of the starting changeset until we find one setting the file to the
revision we are trying to create.
The performance impact appears acceptable:
- We are walking the changelog once for each filelog traversal (as there should
be no overlap between searches),
- changelog traversal itself is fairly cheap, compared to what is likely going
to be perform on the result on the filelog traversal,
- We only touch the manifest for ancestors touching the file, And such
changesets are likely to be the one introducing the file. (except in
pathological cases involving merge),
- We use manifest diff instead of full manifest unpacking to check manifest
content, so it does not involve applying multiple diffs in most case.
- linkrev shadowing is not the common case.
Tests for fixed issues in log, annotate and rename detection have been
added.
But this changeset does not solve all problems. It fixes -ancestry-
computation, but if the linkrev-shadowed changesets is the starting one, we'll
still get things wrong. We'll have to fix the bootstrapping of such operations
in a later changeset. Also, the usage of `hg log FILE` without --follow still
has issues with linkrev pointing to hidden changesets, because it relies on the
`filelog` revset which implement its own traversal logic that is still to be
fixed.
Thanks goes to:
- Matt Mackall: for nudging me in the right direction
- Julien Cristau and Rémi Cardona: for keep telling me linkrev bug were an
evolution show stopper for 3 years.
- Durham Goode: for finding a new linkrev issue every few weeks
- Mads Kiilerich: for that last rename bug who raise this topic over my
anoyance limit.
#require killdaemons
Preparing the subrepository 'sub'
$ hg init sub
$ echo sub > sub/sub
$ hg add -R sub
adding sub/sub (glob)
$ hg commit -R sub -m "sub import"
Preparing the 'main' repo which depends on the subrepo 'sub'
$ hg init main
$ echo main > main/main
$ echo "sub = ../sub" > main/.hgsub
$ hg clone sub main/sub
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg add -R main
adding main/.hgsub (glob)
adding main/main (glob)
$ hg commit -R main -m "main import"
Cleaning both repositories, just as a clone -U
$ hg up -C -R sub null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg up -C -R main null
0 files updated, 0 files merged, 3 files removed, 0 files unresolved
$ rm -rf main/sub
hide outer repo
$ hg init
Serving them both using hgweb
$ printf '[paths]\n/main = main\nsub = sub\n' > webdir.conf
$ hg serve --webdir-conf webdir.conf -a localhost -p $HGPORT \
> -A /dev/null -E /dev/null --pid-file hg.pid -d
$ cat hg.pid >> $DAEMON_PIDS
Clone main from hgweb
$ hg clone "http://localhost:$HGPORT/main" cloned
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 3 changes to 3 files
updating to branch default
cloning subrepo sub from http://localhost:$HGPORT/sub
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
Checking cloned repo ids
$ hg id -R cloned
fdfeeb3e979e tip
$ hg id -R cloned/sub
863c1745b441 tip
subrepo debug for 'main' clone
$ hg debugsub -R cloned
path sub
source ../sub
revision 863c1745b441bd97a8c4a096e87793073f4fb215
$ "$TESTDIR/killdaemons.py" $DAEMON_PIDS
subrepo paths with ssh urls
$ hg clone -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/cloned sshclone
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 3 changes to 3 files
updating to branch default
cloning subrepo sub from ssh://user@dummy/sub
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg -R sshclone push -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/`pwd`/cloned
pushing to ssh://user@dummy/$TESTTMP/cloned
pushing subrepo sub to ssh://user@dummy/$TESTTMP/sub
searching for changes
no changes found
searching for changes
no changes found
[1]
$ cat dummylog
Got arguments 1:user@dummy 2:hg -R cloned serve --stdio
Got arguments 1:user@dummy 2:hg -R sub serve --stdio
Got arguments 1:user@dummy 2:hg -R $TESTTMP/cloned serve --stdio
Got arguments 1:user@dummy 2:hg -R $TESTTMP/sub serve --stdio