[PATCH RFC] changegroup: leave out all parent file revisions when creating bundles

[Mads Kiilerich]

On 10/11/19 7:57 PM, Mads Kiilerich wrote:
> # HG changeset patch
> # User Mads Kiilerich <madski at unity3d.com>
> # Date 1570804632 -7200
> #      Fri Oct 11 16:37:12 2019 +0200
> # Node ID 72d12ee773795edc163f73b9160e5d29022878dd
> # Parent  52781d57313d512efb7150603104bea3ca11d0eb
> changegroup: leave out all parent file revisions when creating bundles

I'm not sure the analysis nailed the root cause. It is tricky to 
reproduce good test cases.

But one problem we could fix by pruning ancestors instead of using linkrevs:

Create a repo with aliasing:

   $ hg init repo1
   $ cd repo1
   $ touch f
   $ hg ci -Aqm 0
   $ echo 1 > f
   $ hg ci -m 1f1
   $ hg up -cqr 0
   $ hg branch -q b
   $ echo 1 > f  # linkrev aliasing to rev 1
   $ hg ci -m 2f1

When bundling rev 2 for a repo that has rev 1, f will be skipped even 
though it
isn't an ancestor:

   $ hg bundle -v -r 2 --base 1 bundle.hg
   1 changesets found
   uncompressed size of bundle content:
        185 (changelog)
        163 (manifests)

A bundle with missing ancestor revisions would fail unbundling with "abort:
00changelog.i at d681519c3ea7: unknown parent!". But if using 
fastpathlinkrev and
the ancestors are present but the file revs are not, the bundle can be 
applied
but will break on use:

   $ hg clone -qU . -r 0 repo2
   $ hg -R repo2 pull bundle.hg
   pulling from bundle.hg
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 0 changes to 0 files
   new changesets 5e690c649d09 (1 drafts)
   (run 'hg update' to get a working copy)
   $ hg -R repo2 up -r tip
   abort: data/f.i at d0c79e1d3309: no match found!
   [255]


/Mads