Patchwork D8721: scmutil: allowing different files to be prefetched per revision

diff --git a/mercurial/subrepo.py b/mercurial/subrepo.py
--- a/mercurial/subrepo.py
+++ b/mercurial/subrepo.py
@@ -639,7 +639,7 @@ 
         rev = self._state[1]
         ctx = self._repo[rev]
         scmutil.prefetchfiles(
-            self._repo, [ctx.rev()], scmutil.matchfiles(self._repo, files)
+            self._repo, [(ctx.rev(), scmutil.matchfiles(self._repo, files))]
         )
         total = abstractsubrepo.archive(self, archiver, prefix, match)
         for subpath in ctx.substate:
diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -1880,18 +1880,30 @@ 
 ]
 
 
-def prefetchfiles(repo, revs, match):
+def prefetchfiles(repo, revmatches):
     """Invokes the registered file prefetch functions, allowing extensions to
     ensure the corresponding files are available locally, before the command
-    uses them."""
-    if match:
-        # The command itself will complain about files that don't exist, so
-        # don't duplicate the message.
-        match = matchmod.badmatch(match, lambda fn, msg: None)
-    else:
-        match = matchall(repo)
+    uses them.
 
-    fileprefetchhooks(repo, revs, match)
+    Args:
+      revmatches: a list of (revision, match) tuples to indicate the files to
+      fetch at each revision. If any of the match elements is None, it matches
+      all files.
+    """
+    def _matcher(m):
+        if m:
+            assert isinstance(m, matchmod.basematcher)
+            # The command itself will complain about files that don't exist, so
+            # don't duplicate the message.
+            return matchmod.badmatch(m, lambda fn, msg: None)
+        else:
+            return matchall(repo)
+
+    revbadmatches = [
+        (rev, _matcher(match)) for (rev, match) in revmatches
+    ]
+
+    fileprefetchhooks(repo, revbadmatches)
 
 
 # a list of (repo, revs, match) prefetch functions
diff --git a/mercurial/patch.py b/mercurial/patch.py
--- a/mercurial/patch.py
+++ b/mercurial/patch.py
@@ -2666,7 +2666,11 @@ 
     prefetchmatch = scmutil.matchfiles(
         repo, list(modifiedset | addedset | removedset)
     )
-    scmutil.prefetchfiles(repo, [ctx1.rev(), ctx2.rev()], prefetchmatch)
+    revmatches = [
+        (ctx1.rev(), prefetchmatch),
+        (ctx2.rev(), prefetchmatch),
+    ]
+    scmutil.prefetchfiles(repo, revmatches)
 
     def difffn(opts, losedata):
         return trydiff(
diff --git a/mercurial/merge.py b/mercurial/merge.py
--- a/mercurial/merge.py
+++ b/mercurial/merge.py
@@ -1121,8 +1121,9 @@ 
     matchfiles = scmutil.matchfiles
     prefetch(
         repo,
-        [ctx.rev()],
-        matchfiles(repo, [f for sublist in oplist for f, args, msg in sublist]),
+        [(ctx.rev(),
+          matchfiles(repo,
+                     [f for sublist in oplist for f, args, msg in sublist]))],
     )
 
 
diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -2540,8 +2540,8 @@ 
         # using things like remotefilelog.
         scmutil.prefetchfiles(
             self.repo(),
-            [self.p1().rev()],
-            scmutil.matchfiles(self.repo(), self._cache.keys()),
+            [(self.p1().rev(),
+              scmutil.matchfiles(self.repo(), self._cache.keys()))],
         )
 
         for path in self._cache.keys():
diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -2138,7 +2138,9 @@ 
         for file in repo[rev].files():
             if not match or match(file):
                 allfiles.add(file)
-    scmutil.prefetchfiles(repo, revs, scmutil.matchfiles(repo, allfiles))
+    match = scmutil.matchfiles(repo, allfiles)
+    revmatches = [(rev, match) for rev in revs]
+    scmutil.prefetchfiles(repo, revmatches)
 
 
 def export(
@@ -2997,14 +2999,14 @@ 
         try:
             if mfnode and mfl[mfnode].find(file)[0]:
                 if _catfmtneedsdata(basefm):
-                    scmutil.prefetchfiles(repo, [ctx.rev()], matcher)
+                    scmutil.prefetchfiles(repo, [(ctx.rev(), matcher)])
                 write(file)
                 return 0
         except KeyError:
             pass
 
     if _catfmtneedsdata(basefm):
-        scmutil.prefetchfiles(repo, [ctx.rev()], matcher)
+        scmutil.prefetchfiles(repo, [(ctx.rev(), matcher)])
 
     for abs in ctx.walk(matcher):
         write(abs)
@@ -3769,11 +3771,11 @@ 
             needdata = (b'revert', b'add', b'undelete')
             oplist = [actions[name][0] for name in needdata]
             prefetch = scmutil.prefetchfiles
-            matchfiles = scmutil.matchfiles
+            matchfiles = scmutil.matchfiles(
+                repo, [f for sublist in oplist for f in sublist])
             prefetch(
                 repo,
-                [ctx.rev()],
-                matchfiles(repo, [f for sublist in oplist for f in sublist]),
+                [(ctx.rev(), matchfiles)],
             )
             match = scmutil.match(repo[None], pats)
             _performrevert(
diff --git a/mercurial/archival.py b/mercurial/archival.py
--- a/mercurial/archival.py
+++ b/mercurial/archival.py
@@ -364,7 +364,7 @@ 
     if total:
         files.sort()
         scmutil.prefetchfiles(
-            repo, [ctx.rev()], scmutil.matchfiles(repo, files)
+            repo, [(ctx.rev(), scmutil.matchfiles(repo, files))]
         )
         progress = repo.ui.makeprogress(
             _(b'archiving'), unit=_(b'files'), total=total
diff --git a/hgext/remotefilelog/__init__.py b/hgext/remotefilelog/__init__.py
--- a/hgext/remotefilelog/__init__.py
+++ b/hgext/remotefilelog/__init__.py
@@ -1118,10 +1118,10 @@ 
     return orig(repo, remote, *args, **kwargs)
 
 
-def _fileprefetchhook(repo, revs, match):
+def _fileprefetchhook(repo, revmatches):
     if isenabled(repo):
         allfiles = []
-        for rev in revs:
+        for rev, match in revmatches:
             if rev == nodemod.wdirrev or rev is None:
                 continue
             ctx = repo[rev]
diff --git a/hgext/lfs/wrapper.py b/hgext/lfs/wrapper.py
--- a/hgext/lfs/wrapper.py
+++ b/hgext/lfs/wrapper.py
@@ -337,7 +337,7 @@ 
             setattr(self, name, getattr(othervfs, name))
 
 
-def _prefetchfiles(repo, revs, match):
+def _prefetchfiles(repo, revmatches):
     """Ensure that required LFS blobs are present, fetching them as a group if
     needed."""
     if not util.safehasattr(repo.svfs, b'lfslocalblobstore'):
@@ -347,7 +347,7 @@ 
     oids = set()
     localstore = repo.svfs.lfslocalblobstore
 
-    for rev in revs:
+    for rev, match in revmatches:
         ctx = repo[rev]
         for f in ctx.walk(match):
             p = pointerfromctx(ctx, f)