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.
$ hg init t
$ cd t
$ echo 1 > foo
$ hg ci -Am1 # 0
adding foo
$ hg branch branchA
marked working directory as branch branchA
(branches are permanent and global, did you want a bookmark?)
$ echo a1 > foo
$ hg ci -ma1 # 1
$ cd ..
$ hg init tt
$ cd tt
$ hg pull ../t
pulling from ../t
requesting all changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
(run 'hg update' to get a working copy)
$ hg up branchA
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd ../t
$ echo a2 > foo
$ hg ci -ma2 # 2
Create branch B:
$ hg up 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg branch branchB
marked working directory as branch branchB
(branches are permanent and global, did you want a bookmark?)
$ echo b1 > foo
$ hg ci -mb1 # 3
$ cd ../tt
A new branch is there
$ hg pull -u ../t
pulling from ../t
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files (+1 heads)
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
Develop both branches:
$ cd ../t
$ hg up branchA
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo a3 > foo
$ hg ci -ma3 # 4
$ hg up branchB
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo b2 > foo
$ hg ci -mb2 # 5
$ cd ../tt
Should succeed, no new heads:
$ hg pull -u ../t
pulling from ../t
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
Add a head on other branch:
$ cd ../t
$ hg up branchA
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo a4 > foo
$ hg ci -ma4 # 6
$ hg up branchB
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo b3.1 > foo
$ hg ci -m b3.1 # 7
$ hg up 5
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo b3.2 > foo
$ hg ci -m b3.2 # 8
created new head
$ cd ../tt
Should succeed because there is only one head on our branch:
$ hg pull -u ../t
pulling from ../t
searching for changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 1 files (+1 heads)
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd ../t
$ hg up -C branchA
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo a5.1 > foo
$ hg ci -ma5.1 # 9
$ hg up 6
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo a5.2 > foo
$ hg ci -ma5.2 # 10
created new head
$ hg up 7
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo b4.1 > foo
$ hg ci -m b4.1 # 11
$ hg up -C 8
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo b4.2 > foo
$ hg ci -m b4.2 # 12
$ cd ../tt
$ hg pull -u ../t
pulling from ../t
searching for changes
adding changesets
adding manifests
adding file changes
added 4 changesets with 4 changes to 1 files (+1 heads)
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
Make changes on new branch on tt
$ hg up 6
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg branch branchC
marked working directory as branch branchC
(branches are permanent and global, did you want a bookmark?)
$ echo b1 > bar
$ hg ci -Am "commit on branchC on tt"
adding bar
Make changes on default branch on t
$ cd ../t
$ hg up -C default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo a1 > bar
$ hg ci -Am "commit on default on t"
adding bar
Pull branchC from tt
$ hg pull ../tt
pulling from ../tt
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
(run 'hg heads' to see heads)
Make changes on default and branchC on tt
$ cd ../tt
$ hg pull ../t
pulling from ../t
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
(run 'hg heads' to see heads)
$ hg up -C default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo a1 > bar1
$ hg ci -Am "commit on default on tt"
adding bar1
$ hg up branchC
2 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo a1 > bar2
$ hg ci -Am "commit on branchC on tt"
adding bar2
Make changes on default and branchC on t
$ cd ../t
$ hg up default
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo a1 > bar3
$ hg ci -Am "commit on default on t"
adding bar3
$ hg up branchC
2 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo a1 > bar4
$ hg ci -Am "commit on branchC on tt"
adding bar4
Pull from tt
$ hg pull ../tt
pulling from ../tt
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 2 files (+2 heads)
(run 'hg heads .' to see heads, 'hg merge' to merge)
$ cd ..