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.
Criss cross merging
$ hg init criss-cross
$ cd criss-cross
$ echo '0 base' > f1
$ echo '0 base' > f2
$ hg ci -Aqm '0 base'
$ echo '1 first change' > f1
$ hg ci -m '1 first change f1'
$ hg up -qr0
$ echo '2 first change' > f2
$ hg ci -qm '2 first change f2'
$ hg merge -qr 1
$ hg ci -m '3 merge'
$ hg up -qr2
$ hg merge -qr1
$ hg ci -qm '4 merge'
$ echo '5 second change' > f1
$ hg ci -m '5 second change f1'
$ hg up -r3
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo '6 second change' > f2
$ hg ci -m '6 second change f2'
$ hg log -G
@ changeset: 6:3b08d01b0ab5
| tag: tip
| parent: 3:cf89f02107e5
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: 6 second change f2
|
| o changeset: 5:adfe50279922
| | user: test
| | date: Thu Jan 01 00:00:00 1970 +0000
| | summary: 5 second change f1
| |
| o changeset: 4:7d3e55501ae6
| |\ parent: 2:40663881a6dd
| | | parent: 1:0f6b37dbe527
| | | user: test
| | | date: Thu Jan 01 00:00:00 1970 +0000
| | | summary: 4 merge
| | |
o---+ changeset: 3:cf89f02107e5
| | | parent: 2:40663881a6dd
|/ / parent: 1:0f6b37dbe527
| | user: test
| | date: Thu Jan 01 00:00:00 1970 +0000
| | summary: 3 merge
| |
| o changeset: 2:40663881a6dd
| | parent: 0:40494bf2444c
| | user: test
| | date: Thu Jan 01 00:00:00 1970 +0000
| | summary: 2 first change f2
| |
o | changeset: 1:0f6b37dbe527
|/ user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: 1 first change f1
|
o changeset: 0:40494bf2444c
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0 base
$ hg merge -v --debug --tool internal:dump 5 --config merge.preferancestor='!'
note: using 0f6b37dbe527 as ancestor of 3b08d01b0ab5 and adfe50279922
alternatively, use --config merge.preferancestor=40663881a6dd
searching for copies back to rev 3
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 0f6b37dbe527, local: 3b08d01b0ab5+, remote: adfe50279922
preserving f2 for resolve of f2
f1: remote is newer -> g
getting f1
updating: f1 1/2 files (50.00%)
f2: versions differ -> m
updating: f2 2/2 files (100.00%)
picked tool 'internal:dump' for f2 (binary False symlink False)
merging f2
my f2@3b08d01b0ab5+ other f2@adfe50279922 ancestor f2@40494bf2444c
1 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg update -C .' to abandon
[1]
$ head *
==> f1 <==
5 second change
==> f2 <==
6 second change
==> f2.base <==
0 base
==> f2.local <==
6 second change
==> f2.orig <==
6 second change
==> f2.other <==
2 first change
$ hg up -qC .
$ hg merge -v --tool internal:dump 5 --config merge.preferancestor="null 40663881 3b08d"
note: using 40663881a6dd as ancestor of 3b08d01b0ab5 and adfe50279922
alternatively, use --config merge.preferancestor=0f6b37dbe527
resolving manifests
merging f1
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg update -C .' to abandon
[1]
Redo merge with merge.preferancestor="*" to enable bid merge
$ rm f*
$ hg up -qC .
$ hg merge -v --debug --tool internal:dump 5 --config merge.preferancestor="*"
note: merging 3b08d01b0ab5+ and adfe50279922 using bids from ancestors 0f6b37dbe527 and 40663881a6dd
calculating bids for ancestor 0f6b37dbe527
searching for copies back to rev 3
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 0f6b37dbe527, local: 3b08d01b0ab5+, remote: adfe50279922
f1: remote is newer -> g
f2: versions differ -> m
calculating bids for ancestor 40663881a6dd
searching for copies back to rev 3
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 40663881a6dd, local: 3b08d01b0ab5+, remote: adfe50279922
f1: versions differ -> m
f2: remote unchanged -> k
auction for merging merge bids
f1: picking 'get' action
f2: picking 'keep' action
end of auction
f1: remote is newer -> g
getting f1
updating: f1 1/1 files (100.00%)
f2: remote unchanged -> k
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ head *
==> f1 <==
5 second change
==> f2 <==
6 second change
The other way around:
$ hg up -C -r5
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg merge -v --debug --config merge.preferancestor="*"
note: merging adfe50279922+ and 3b08d01b0ab5 using bids from ancestors 0f6b37dbe527 and 40663881a6dd
calculating bids for ancestor 0f6b37dbe527
searching for copies back to rev 3
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 0f6b37dbe527, local: adfe50279922+, remote: 3b08d01b0ab5
f1: remote unchanged -> k
f2: versions differ -> m
calculating bids for ancestor 40663881a6dd
searching for copies back to rev 3
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 40663881a6dd, local: adfe50279922+, remote: 3b08d01b0ab5
f1: versions differ -> m
f2: remote is newer -> g
auction for merging merge bids
f1: picking 'keep' action
f2: picking 'get' action
end of auction
f2: remote is newer -> g
getting f2
updating: f2 1/1 files (100.00%)
f1: remote unchanged -> k
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ head *
==> f1 <==
5 second change
==> f2 <==
6 second change
Verify how the output looks and and how verbose it is:
$ hg up -qC
$ hg merge
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg up -qC
$ hg merge -v
note: merging 3b08d01b0ab5+ and adfe50279922 using bids from ancestors 0f6b37dbe527 and 40663881a6dd
calculating bids for ancestor 0f6b37dbe527
resolving manifests
calculating bids for ancestor 40663881a6dd
resolving manifests
auction for merging merge bids
f1: picking 'get' action
f2: picking 'keep' action
end of auction
getting f1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg up -qC
$ hg merge -v --debug --config merge.preferancestor="*"
note: merging 3b08d01b0ab5+ and adfe50279922 using bids from ancestors 0f6b37dbe527 and 40663881a6dd
calculating bids for ancestor 0f6b37dbe527
searching for copies back to rev 3
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 0f6b37dbe527, local: 3b08d01b0ab5+, remote: adfe50279922
f1: remote is newer -> g
f2: versions differ -> m
calculating bids for ancestor 40663881a6dd
searching for copies back to rev 3
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 40663881a6dd, local: 3b08d01b0ab5+, remote: adfe50279922
f1: versions differ -> m
f2: remote unchanged -> k
auction for merging merge bids
f1: picking 'get' action
f2: picking 'keep' action
end of auction
f1: remote is newer -> g
getting f1
updating: f1 1/1 files (100.00%)
f2: remote unchanged -> k
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cd ..
http://stackoverflow.com/questions/9350005/how-do-i-specify-a-merge-base-to-use-in-a-hg-merge/9430810
$ hg init ancestor-merging
$ cd ancestor-merging
$ echo a > x
$ hg commit -A -m a x
$ hg update -q 0
$ echo b >> x
$ hg commit -m b
$ hg update -q 0
$ echo c >> x
$ hg commit -qm c
$ hg update -q 1
$ hg merge -q --tool internal:local 2
$ echo c >> x
$ hg commit -m bc
$ hg update -q 2
$ hg merge -q --tool internal:local 1
$ echo b >> x
$ hg commit -qm cb
$ hg merge --config merge.preferancestor='!'
note: using 70008a2163f6 as ancestor of 0d355fdef312 and 4b8b546a3eef
alternatively, use --config merge.preferancestor=b211bbc6eb3c
merging x
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat x
a
c
b
c
$ hg up -qC .
$ hg merge --config merge.preferancestor=b211bbc6eb3c
note: using b211bbc6eb3c as ancestor of 0d355fdef312 and 4b8b546a3eef
alternatively, use --config merge.preferancestor=70008a2163f6
merging x
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat x
a
b
c
b
$ hg up -qC .
$ hg merge -v --config merge.preferancestor="*"
note: merging 0d355fdef312+ and 4b8b546a3eef using bids from ancestors 70008a2163f6 and b211bbc6eb3c
calculating bids for ancestor 70008a2163f6
resolving manifests
calculating bids for ancestor b211bbc6eb3c
resolving manifests
auction for merging merge bids
x: multiple bids for merge action:
versions differ -> m
versions differ -> m
x: ambiguous merge - picked m action
end of auction
merging x
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ cat x
a
c
b
c
Verify that the old context ancestor works with / despite preferancestor:
$ hg log -r 'ancestor(head())' --config merge.preferancestor=1 -T '{rev}\n'
1
$ hg log -r 'ancestor(head())' --config merge.preferancestor=2 -T '{rev}\n'
2
$ hg log -r 'ancestor(head())' --config merge.preferancestor=3 -T '{rev}\n'
1
$ hg log -r 'ancestor(head())' --config merge.preferancestor='1337 * - 2' -T '{rev}\n'
2
$ cd ..