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shelve: use matcher to restrict prefetch to just the modified files
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Authored by spectral on Nov 13 2018, 9:09 PM.

Details

Summary

Shelve currently operates by:

  • make a temp commit
  • identify all the bases necessary to shelve, put them in the bundle
  • use exportfile to export the temp commit to the bundle ('file' here means "export to this fd", not "export this file")
  • remove the temp commit

exportfile calls prefetchfiles, and prefetchfiles uses a matcher to restrict
what files it's going to prefetch; if it's not provided, it's alwaysmatcher.
This means that hg shelve in a remotefilelog repo can possibly download the
file contents of everything in the repository, even when it doesn't need to. It
luckily is restricted to the narrowspec (if there is one), but this is still a
lot of downloading that's just unnecessary, especially if there's a "smart"
VCS-aware filesystem involved.

exportfile is called with exactly one revision to emit, so we're just
restricting it to prefetching the files from that revision. The base revisions
having separate files should not be a concern since they're handled already;
example:

commit 10 is draft and modifies foo/a.txt and foo/b.txt
commit 11 is draft and modifies foo/a.txt
my working directory that I'm shelving modifies foo/b.txt

By the time we get to exportfile, commit 10 and 11 are already handled, so the
matcher only specifying foo/b.txt does not cause any problems. I verified this
by doing an hg unbundle on the bundle that shelve produces, and getting the
full contents of those commits back out, instead of just the files that were
modified in the shelve.

Diff Detail

Repository
rHG Mercurial
Lint
Automatic diff as part of commit; lint not applicable.
Unit
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

spectral created this revision.Nov 13 2018, 9:09 PM
yuja added a subscriber: yuja.Nov 14 2018, 8:02 AM

+ # Create a matcher so that prefetch doesn't attempt to fetch the entire
+ # repository pointlessly.
+ match = scmutil.matchfiles(repo, repo[node].files())

with shelvedfile(repo, name, patchextension).opener('wb') as fp:
  • cmdutil.exportfile(repo, [node], fp, opts=mdiff.diffopts(git=True))

+ cmdutil.exportfile(repo, [node], fp, opts=mdiff.diffopts(git=True),
+ match=match)

Seems fine as the temporary commit shouldn't be a merge, so the .files()
should include all changes.

Queued, thanks.

This revision was automatically updated to reflect the committed changes.