tests/test-issue672.t

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

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.

Differential Revision: https://phab.mercurial-scm.org/D5268

https://bz.mercurial-scm.org/672

# 0-2-4
#  \ \ \
#   1-3-5
#
# rename in #1, content change in #4.

  $ hg init

  $ touch 1
  $ touch 2
  $ hg commit -Am init  # 0
  adding 1
  adding 2

  $ hg rename 1 1a
  $ hg commit -m rename # 1

  $ hg co -C 0
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo unrelated >> 2
  $ hg ci -m unrelated1 # 2
  created new head

  $ hg merge --debug 1
    searching for copies back to rev 1
    unmatched files in other:
     1a
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: '1' -> dst: '1a' 
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: 81f4b099af3d, local: c64f439569a9+, remote: c12dcd37c90a
   1: other deleted -> r
  removing 1
   1a: remote created -> g
  getting 1a
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg ci -m merge1 # 3

  $ hg co -C 2
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ echo hello >> 1
  $ hg ci -m unrelated2 # 4
  created new head

  $ hg co -C 3
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ hg merge -y --debug 4
    searching for copies back to rev 1
    unmatched files in local:
     1a
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: '1' -> dst: '1a' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: c64f439569a9, local: e327dca35ac8+, remote: 746e9549ea96
   preserving 1a for resolve of 1a
  starting 4 threads for background file closing (?)
   1a: local copied/moved from 1 -> m (premerge)
  picked tool ':merge' for 1a (binary False symlink False changedelete False)
  merging 1a and 1 to 1a
  my 1a@e327dca35ac8+ other 1@746e9549ea96 ancestor 1@c64f439569a9
   premerge successful
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg co -C 4
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ hg merge -y --debug 3
    searching for copies back to rev 1
    unmatched files in other:
     1a
    all copies found (* = to merge, ! = divergent, % = renamed and deleted):
     src: '1' -> dst: '1a' *
    checking for directory renames
  resolving manifests
   branchmerge: True, force: False, partial: False
   ancestor: c64f439569a9, local: 746e9549ea96+, remote: e327dca35ac8
   preserving 1 for resolve of 1a
  removing 1
  starting 4 threads for background file closing (?)
   1a: remote moved from 1 -> m (premerge)
  picked tool ':merge' for 1a (binary False symlink False changedelete False)
  merging 1 and 1a to 1a
  my 1a@746e9549ea96+ other 1a@e327dca35ac8 ancestor 1@c64f439569a9
   premerge successful
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)