tests/test-diff-copy-depth.t

templatekw: allow getlatesttags() to match a specific tag pattern

This will allow the latest class of tag to be found, such as a release candidate
or final build, instead of just the absolute latest.  It will be exposed in a
future patch.

It's unfortunate that the original 'latesttags' cache can't be used to determine
the proper values, but it isn't fully populated for the entire repo.  For
example, the {latesttagdistance} keyword on the Mecurial repo builds the cache
up back to the revision for 1.4.  If the pattern was 're:^0\.\d$', that wouldn't
be in the cache.  Maybe this can be optimized some other way, but for now, this
is the simpliest implementation.

  $ for i in aaa zzz; do
  >     hg init t
  >     cd t
  > 
  >     echo
  >     echo "-- With $i"
  > 
  >     touch file
  >     hg add file
  >     hg ci -m "Add"
  > 
  >     hg cp file $i
  >     hg ci -m "a -> $i"
  > 
  >     hg cp $i other-file
  >     echo "different" >> $i
  >     hg ci -m "$i -> other-file"
  > 
  >     hg cp other-file somename
  > 
  >     echo "Status":
  >     hg st -C
  >     echo
  >     echo "Diff:"
  >     hg diff -g
  > 
  >     cd ..
  >     rm -rf t
  > done
  
  -- With aaa
  Status:
  A somename
    other-file
  
  Diff:
  diff --git a/other-file b/somename
  copy from other-file
  copy to somename
  
  -- With zzz
  Status:
  A somename
    other-file
  
  Diff:
  diff --git a/other-file b/somename
  copy from other-file
  copy to somename