revset: add the 'subrepo' symbol

This returns the csets where matching subrepos have changed with respect to the
containing repo's first parent.  The second parent shouldn't matter, because it
is either syncing up to the first parent (i.e. it hasn't changed from the
current branch's POV), or the merge changed it with respect to the first parent
(which already adds it to the set).

There's already a 'subrepo' fileset, but it is prefixed with 'set:', so there
should be no ambiguity (in code anyway).  The only test I see for it is to
revert subrepos named by a glob pattern (in test-subrepo.t, line 58).  Since it
doesn't return a tracked file, neither 'log "set:subrepo()"' nor
'files "set:subrepo()"' print anything.  Therefore, it seems useful to have a
revset that will return something for log (and can be added to a revsetalias to
be chained with 'file' revsets.)

It might be nice to be able to filter for added, modified and removed
separately, but add/remove should be rare.  It might also be nice to be able to
do a 'contains' check, in addition to this mutated check.  Maybe it is possible
to get those with the existing 'adds', 'contains', 'modifies' and 'removes' by
teaching them to chase explicit paths into subrepos.

I'm not sure if this should be added to the 'modifies adds removes' line in
revset.optimize() (since it is doing an AMR check on .hgsubstate), or if it is
OK to put into 'safesymbols' (things like 'file' are on the list, and that takes
a regex, among other patterns).

mercurial/revset.py

@@ -1755,6 +1755,49 b' def sort(repo, subset, x):'
     l.sort()
     return baseset([e[-1] for e in l])
 
+def subrepo(repo, subset, x):
+    """``subrepo([pattern])``
+    Changesets that add, modify or remove the given subrepo.  If no subrepo
+    pattern is named, any subrepo changes are returned.
+    """
+    # i18n: "subrepo" is a keyword
+    args = getargs(x, 0, 1, _('subrepo takes at most one argument'))
+    if len(args) != 0:
+        pat = getstring(args[0], _("subrepo requires a pattern"))
+
+    m = matchmod.exact(repo.root, repo.root, ['.hgsubstate'])
+
+    def submatches(names):
+        k, p, m = _stringmatcher(pat)
+        for name in names:
+            if m(name):
+                yield name
+
+    def matches(x):
+        c = repo[x]
+        s = repo.status(c.p1().node(), c.node(), match=m)
+
+        if len(args) == 0:
+            return s.added or s.modified or s.removed
+
+        if s.added:
+            return util.any(submatches(c.substate.keys()))
+
+        if s.modified:
+            subs = set(c.p1().substate.keys())
+            subs.update(c.substate.keys())
+
+            for path in submatches(subs):
+                if c.p1().substate.get(path) != c.substate.get(path):
+                    return True
+
+        if s.removed:
+            return util.any(submatches(c.p1().substate.keys()))
+
+        return False
+
+    return subset.filter(matches)
+
 def _stringmatcher(pattern):
     """
     accepts a string, possibly starting with 're:' or 'literal:' prefix.
@@ -1952,6 +1995,7 b' symbols = {'
     "roots": roots,
     "sort": sort,
     "secret": secret,
+    "subrepo": subrepo,
     "matching": matching,
     "tag": tag,
     "tagged": tagged,

tests/test-subrepo-deep-nested-change.t

@@ -458,4 +458,85 b' Test a directory commit with a changed l'
   R a.dat
   R foo/bar/abc
 
+
+  $ echo foo > main
+  $ hg ci -m "mod parent only"
+  $ hg init sub3
+  $ echo "sub3 = sub3" >> .hgsub
+  $ echo xyz > sub3/a.txt
+  $ hg add sub3/a.txt
+  $ hg ci -Sm "add sub3"
+  committing subrepository sub3
+  $ cat .hgsub | grep -v sub3 > .hgsub1
+  $ mv .hgsub1 .hgsub
+  $ hg ci -m "remove sub3"
+
+  $ hg log -r "subrepo()" --style compact
+  0   7f491f53a367   1970-01-01 00:00 +0000   test
+    main import
+  
+  1   ffe6649062fe   1970-01-01 00:00 +0000   test
+    deep nested modif should trigger a commit
+  
+  2   9bb10eebee29   1970-01-01 00:00 +0000   test
+    add test.txt
+  
+  3   7c64f035294f   1970-01-01 00:00 +0000   test
+    add large files
+  
+  4   f734a59e2e35   1970-01-01 00:00 +0000   test
+    forget testing
+  
+  11   9685a22af5db   1970-01-01 00:00 +0000   test
+    add sub3
+  
+  12[tip]   2e0485b475b9   1970-01-01 00:00 +0000   test
+    remove sub3
+  
+  $ hg log -r "subrepo('sub3')" --style compact
+  11   9685a22af5db   1970-01-01 00:00 +0000   test
+    add sub3
+  
+  12[tip]   2e0485b475b9   1970-01-01 00:00 +0000   test
+    remove sub3
+  
+  $ hg log -r "subrepo('bogus')" --style compact
+
+
+Test .hgsubstate in the R state
+
+  $ hg rm .hgsub .hgsubstate
+  $ hg ci -m 'trash subrepo tracking'
+
+  $ hg log -r "subrepo('re:sub\d+')" --style compact
+  0   7f491f53a367   1970-01-01 00:00 +0000   test
+    main import
+  
+  1   ffe6649062fe   1970-01-01 00:00 +0000   test
+    deep nested modif should trigger a commit
+  
+  2   9bb10eebee29   1970-01-01 00:00 +0000   test
+    add test.txt
+  
+  3   7c64f035294f   1970-01-01 00:00 +0000   test
+    add large files
+  
+  4   f734a59e2e35   1970-01-01 00:00 +0000   test
+    forget testing
+  
+  11   9685a22af5db   1970-01-01 00:00 +0000   test
+    add sub3
+  
+  12   2e0485b475b9   1970-01-01 00:00 +0000   test
+    remove sub3
+  
+  13[tip]   a68b2c361653   1970-01-01 00:00 +0000   test
+    trash subrepo tracking
+  
+
+Restore the trashed subrepo tracking
+
+  $ hg rollback -q
+  $ hg update -Cq .
+
   $ cd ..