grep: add MULTIREV support to --allfiles flag

This patch facilitates passing multiple revisions with all-files flag.
It's assumed that if you are passing multiple revisions to --allfiles,
you want hits from all of them.

Differential Revision: https://phab.mercurial-scm.org/D3976

mercurial/cmdutil.py

@@ -1889,9 +1889,6 b' def walkchangerevs(repo, match, opts, pr'
     revs = _walkrevs(repo, opts)
     if not revs:
         return []
-    if allfiles and len(revs) > 1:
-        raise error.Abort(_("multiple revisions not supported with "
-                            "--all-files"))
     wanted = set()
     slowpath = match.anypats() or (not match.always() and opts.get('removed'))
     fncache = {}

mercurial/commands.py

@@ -2533,6 +2533,7 b' def grep(ui, repo, pattern, *pats, **opt'
     """
     opts = pycompat.byteskwargs(opts)
     diff = opts.get('all') or opts.get('diff')
+    all_files = opts.get('all_files')
     if diff and opts.get('all_files'):
         raise error.Abort(_('--diff and --all-files are mutually exclusive'))
     # TODO: remove "not opts.get('rev')" if --all-files -rMULTIREV gets working
@@ -2757,7 +2758,7 b' def grep(ui, repo, pattern, *pats, **opt'
             if pstates or states:
                 r = display(fm, fn, ctx, pstates, states)
                 found = found or r
-                if r and not diff:
+                if r and not diff and not all_files:
                     skip[fn] = True
                     if copy:
                         skip[copy] = True

tests/test-grep.t

@@ -491,3 +491,13 b' but it should be available in template d'
   ]
 
   $ cd ..
+
+test -rMULTIREV with --all-files
+
+  $ cd sng
+  $ hg rm um
+  $ hg commit -m "deletes um"
+  $ hg grep -r "0:2" "unmod" --all-files
+  um:0:unmod
+  um:1:unmod
+  $ cd ..