D5268: shelve: use matcher to restrict prefetch to just the modified files

[spectral (Kyle Lippincott)]

spectral created this revision.
Herald added a subscriber: mercurial-devel.
Herald added a reviewer: hg-reviewers.

REVISION 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.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D5268

AFFECTED FILES
  hgext/shelve.py

CHANGE DETAILS

diff --git a/hgext/shelve.py b/hgext/shelve.py
--- a/hgext/shelve.py
+++ b/hgext/shelve.py
@@ -430,8 +430,12 @@
     shelvedfile(repo, name, 'shelve').writeinfo(info)
     bases = list(mutableancestors(repo[node]))
     shelvedfile(repo, name, 'hg').writebundle(bases, node)
+    # 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)
 
 def _includeunknownfiles(repo, pats, opts, extra):
     s = repo.status(match=scmutil.match(repo[None], pats, opts),



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