view tests/test-unionrepo.t @ 23702:c48924787eaa

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.

Test unionrepo functionality

Create one repository

  $ hg init repo1
  $ cd repo1
  $ touch repo1-0
  $ echo repo1-0 > f
  $ hg ci -Aqmrepo1-0
  $ touch repo1-1
  $ echo repo1-1 >> f
  $ hg ci -Aqmrepo1-1
  $ touch repo1-2
  $ echo repo1-2 >> f
  $ hg ci -Aqmrepo1-2
  $ hg log --template '{rev}:{node|short}  {desc|firstline}\n'
  2:68c0685446a3  repo1-2
  1:8a58db72e69d  repo1-1
  0:f093fec0529b  repo1-0
  $ tip1=`hg id -q`
  $ cd ..

- and a clone with a not-completely-trivial history

  $ hg clone -q repo1 --rev 0 repo2
  $ cd repo2
  $ touch repo2-1
  $ sed '1i\
  > repo2-1 at top
  > ' f > f.tmp
  $ mv f.tmp f
  $ hg ci -Aqmrepo2-1
  $ touch repo2-2
  $ hg pull -q ../repo1 -r 1
  $ hg merge -q
  $ hg ci -Aqmrepo2-2-merge
  $ touch repo2-3
  $ echo repo2-3 >> f
  $ hg ci -mrepo2-3
  $ hg log --template '{rev}:{node|short}  {desc|firstline}\n'
  4:2f0d178c469c  repo2-3
  3:9e6fb3e0b9da  repo2-2-merge
  2:8a58db72e69d  repo1-1
  1:c337dba826e7  repo2-1
  0:f093fec0529b  repo1-0
  $ cd ..

revisions from repo2 appear as appended / pulled to repo1

  $ hg -R union:repo1+repo2 log --template '{rev}:{node|short}  {desc|firstline}\n'
  5:2f0d178c469c  repo2-3
  4:9e6fb3e0b9da  repo2-2-merge
  3:c337dba826e7  repo2-1
  2:68c0685446a3  repo1-2
  1:8a58db72e69d  repo1-1
  0:f093fec0529b  repo1-0

manifest can be retrieved for revisions in both repos

  $ hg -R union:repo1+repo2 mani -r $tip1
  f
  repo1-0
  repo1-1
  repo1-2
  $ hg -R union:repo1+repo2 mani -r 4
  f
  repo1-0
  repo1-1
  repo2-1
  repo2-2

files can be retrieved form both repos

  $ hg -R repo1 cat repo1/f -r2
  repo1-0
  repo1-1
  repo1-2

  $ hg -R union:repo1+repo2 cat -r$tip1 repo1/f
  repo1-0
  repo1-1
  repo1-2

  $ hg -R union:repo1+repo2 cat -r4 $TESTTMP/repo1/f
  repo2-1 at top
  repo1-0
  repo1-1

files can be compared across repos

  $ hg -R union:repo1+repo2 diff -r$tip1 -rtip
  diff -r 68c0685446a3 -r 2f0d178c469c f
  --- a/f	Thu Jan 01 00:00:00 1970 +0000
  +++ b/f	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,3 +1,4 @@
  +repo2-1 at top
   repo1-0
   repo1-1
  -repo1-2
  +repo2-3

heads from both repos are found correctly

  $ hg -R union:repo1+repo2 heads --template '{rev}:{node|short}  {desc|firstline}\n'
  5:2f0d178c469c  repo2-3
  2:68c0685446a3  repo1-2

revsets works across repos

  $ hg -R union:repo1+repo2 id -r "ancestor($tip1, 5)"
  8a58db72e69d

annotate works - an indication that linkrevs works

  $ hg --cwd repo1 -Runion:../repo2 annotate $TESTTMP/repo1/f -r tip
  3: repo2-1 at top
  0: repo1-0
  1: repo1-1
  5: repo2-3

union repos can be cloned ... and clones works correctly

  $ hg clone -U union:repo1+repo2 repo3
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 11 changes to 6 files (+1 heads)

  $ hg -R repo3 paths
  default = union:repo1+repo2

  $ hg -R repo3 verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  6 files, 6 changesets, 11 total revisions

  $ hg -R repo3 heads --template '{rev}:{node|short}  {desc|firstline}\n'
  5:2f0d178c469c  repo2-3
  2:68c0685446a3  repo1-2

  $ hg -R repo3 log --template '{rev}:{node|short}  {desc|firstline}\n'
  5:2f0d178c469c  repo2-3
  4:9e6fb3e0b9da  repo2-2-merge
  3:c337dba826e7  repo2-1
  2:68c0685446a3  repo1-2
  1:8a58db72e69d  repo1-1
  0:f093fec0529b  repo1-0