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.
$ cat >> $HGRCPATH <<EOF
> [extensions]
> rebase=
>
> [alias]
> tglog = log -G --template "{rev}: '{desc}' {branches}\n"
> EOF
$ hg init repo
$ cd repo
$ echo A > a
$ echo >> a
$ hg ci -Am A
adding a
$ echo B > a
$ echo >> a
$ hg ci -m B
$ echo C > a
$ echo >> a
$ hg ci -m C
$ hg up -q -C 0
$ echo D >> a
$ hg ci -Am AD
created new head
$ hg tglog
@ 3: 'AD'
|
| o 2: 'C'
| |
| o 1: 'B'
|/
o 0: 'A'
$ hg rebase -s 1 -d 3
rebasing 1:0f4f7cb4f549 "B"
merging a
rebasing 2:30ae917c0e4f "C"
merging a
saved backup bundle to $TESTTMP/repo/.hg/strip-backup/0f4f7cb4f549-backup.hg (glob)
$ hg tglog
o 3: 'C'
|
o 2: 'B'
|
@ 1: 'AD'
|
o 0: 'A'
$ cd ..
Test rebasing of merges with ancestors of the rebase destination - a situation
that often happens when trying to recover from repeated merging with a mainline
branch.
The test case creates a dev branch that contains a couple of merges from the
default branch. When rebasing to the default branch, these merges would be
merges with ancestors on the same branch. The merges _could_ contain some
interesting conflict resolutions or additional changes in the merge commit, but
that is mixed up with the actual merge stuff and there is in general no way to
separate them.
Note: The dev branch contains _no_ changes to f-default. It might be unclear
how rebasing of ancestor merges should be handled, but the current behavior
with spurious prompts for conflicts in files that didn't change seems very
wrong.
$ hg init ancestor-merge
$ cd ancestor-merge
$ touch f-default
$ hg ci -Aqm 'default: create f-default'
$ hg branch -q dev
$ hg ci -qm 'dev: create branch'
$ echo stuff > f-dev
$ hg ci -Aqm 'dev: f-dev stuff'
$ hg up -q default
$ echo stuff > f-default
$ hg ci -m 'default: f-default stuff'
$ hg up -q dev
$ hg merge -q default
$ hg ci -m 'dev: merge default'
$ hg up -q default
$ hg rm f-default
$ hg ci -m 'default: remove f-default'
$ hg up -q dev
$ hg merge -q default
$ hg ci -m 'dev: merge default'
$ hg up -q default
$ echo stuff > f-other
$ hg ci -Aqm 'default: f-other stuff'
$ hg tglog
@ 7: 'default: f-other stuff'
|
| o 6: 'dev: merge default' dev
|/|
o | 5: 'default: remove f-default'
| |
| o 4: 'dev: merge default' dev
|/|
o | 3: 'default: f-default stuff'
| |
| o 2: 'dev: f-dev stuff' dev
| |
| o 1: 'dev: create branch' dev
|/
o 0: 'default: create f-default'
$ hg clone -qU . ../ancestor-merge-2
Full rebase all the way back from branching point:
$ hg rebase -r 'only(dev,default)' -d default
rebasing 1:1d1a643d390e "dev: create branch"
note: rebase of 1:1d1a643d390e created no changes to commit
rebasing 2:ec2c14fb2984 "dev: f-dev stuff"
rebasing 4:4b019212aaf6 "dev: merge default"
remote changed f-default which local deleted
use (c)hanged version or leave (d)eleted? c
rebasing 6:9455ee510502 "dev: merge default"
saved backup bundle to $TESTTMP/ancestor-merge/.hg/strip-backup/1d1a643d390e-backup.hg (glob)
$ hg tglog
o 6: 'dev: merge default'
|
o 5: 'dev: merge default'
|
o 4: 'dev: f-dev stuff'
|
@ 3: 'default: f-other stuff'
|
o 2: 'default: remove f-default'
|
o 1: 'default: f-default stuff'
|
o 0: 'default: create f-default'
Grafty cherry picking rebasing:
$ cd ../ancestor-merge-2
$ hg phase -fdr0:
$ hg rebase -r 'children(only(dev,default))' -d default
rebasing 2:ec2c14fb2984 "dev: f-dev stuff"
rebasing 4:4b019212aaf6 "dev: merge default"
remote changed f-default which local deleted
use (c)hanged version or leave (d)eleted? c
rebasing 6:9455ee510502 "dev: merge default"
saved backup bundle to $TESTTMP/ancestor-merge-2/.hg/strip-backup/ec2c14fb2984-backup.hg (glob)
$ hg tglog
o 7: 'dev: merge default'
|
o 6: 'dev: merge default'
|
o 5: 'dev: f-dev stuff'
|
o 4: 'default: f-other stuff'
|
o 3: 'default: remove f-default'
|
o 2: 'default: f-default stuff'
|
| o 1: 'dev: create branch' dev
|/
o 0: 'default: create f-default'
$ cd ..
Test order of parents of rebased merged with un-rebased changes as p1.
$ hg init parentorder
$ cd parentorder
$ touch f
$ hg ci -Aqm common
$ touch change
$ hg ci -Aqm change
$ touch target
$ hg ci -Aqm target
$ hg up -qr 0
$ touch outside
$ hg ci -Aqm outside
$ hg merge -qr 1
$ hg ci -m 'merge p1 3=outside p2 1=ancestor'
$ hg par
changeset: 4:6990226659be
tag: tip
parent: 3:f59da8fc0fcf
parent: 1:dd40c13f7a6f
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: merge p1 3=outside p2 1=ancestor
$ hg up -qr 1
$ hg merge -qr 3
$ hg ci -qm 'merge p1 1=ancestor p2 3=outside'
$ hg par
changeset: 5:a57575f79074
tag: tip
parent: 1:dd40c13f7a6f
parent: 3:f59da8fc0fcf
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: merge p1 1=ancestor p2 3=outside
$ hg tglog
@ 5: 'merge p1 1=ancestor p2 3=outside'
|\
+---o 4: 'merge p1 3=outside p2 1=ancestor'
| |/
| o 3: 'outside'
| |
+---o 2: 'target'
| |
o | 1: 'change'
|/
o 0: 'common'
$ hg rebase -r 4 -d 2
rebasing 4:6990226659be "merge p1 3=outside p2 1=ancestor"
saved backup bundle to $TESTTMP/parentorder/.hg/strip-backup/6990226659be-backup.hg (glob)
$ hg tip
changeset: 5:cca50676b1c5
tag: tip
parent: 2:a60552eb93fb
parent: 3:f59da8fc0fcf
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: merge p1 3=outside p2 1=ancestor
$ hg rebase -r 4 -d 2
rebasing 4:a57575f79074 "merge p1 1=ancestor p2 3=outside"
saved backup bundle to $TESTTMP/parentorder/.hg/strip-backup/a57575f79074-backup.hg (glob)
$ hg tip
changeset: 5:f9daf77ffe76
tag: tip
parent: 2:a60552eb93fb
parent: 3:f59da8fc0fcf
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: merge p1 1=ancestor p2 3=outside
$ hg tglog
@ 5: 'merge p1 1=ancestor p2 3=outside'
|\
+---o 4: 'merge p1 3=outside p2 1=ancestor'
| |/
| o 3: 'outside'
| |
o | 2: 'target'
| |
o | 1: 'change'
|/
o 0: 'common'
rebase of merge of ancestors
$ hg up -qr 2
$ hg merge -qr 3
$ echo 'other change while merging future "rebase ancestors"' > other
$ hg ci -Aqm 'merge rebase ancestors'
$ hg rebase -d 5 -v
rebasing 6:4c5f12f25ebe "merge rebase ancestors" (tip)
resolving manifests
removing other
note: merging f9daf77ffe76+ and 4c5f12f25ebe using bids from ancestors a60552eb93fb and f59da8fc0fcf
calculating bids for ancestor a60552eb93fb
resolving manifests
calculating bids for ancestor f59da8fc0fcf
resolving manifests
auction for merging merge bids
other: consensus for g
end of auction
getting other
other
rebase merging completed
1 changesets found
saved backup bundle to $TESTTMP/parentorder/.hg/strip-backup/4c5f12f25ebe-backup.hg (glob)
1 changesets found
adding branch
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
rebase completed
$ hg tglog
@ 6: 'merge rebase ancestors'
|
o 5: 'merge p1 1=ancestor p2 3=outside'
|\
+---o 4: 'merge p1 3=outside p2 1=ancestor'
| |/
| o 3: 'outside'
| |
o | 2: 'target'
| |
o | 1: 'change'
|/
o 0: 'common'