copies: add an devel option to trace all files

Filelog based copy tracing only trace copy for file that have been added. This
is a trade off between skipping some rare copy case in exchange for avoiding
atrocious-to-the-point-of-unusable performance.

The changeset centric copy tracing does not need this trade off and naturally
trace all copy, include the one involving non-new files.

In order to ease the comparison from both algorithm, we add a small devel option
to trace copy for all files in the target revisions.

Differential Revision: https://phab.mercurial-scm.org/D9796

mercurial/configitems.py

@@ -615,6 +615,12 b' coreconfigitem('
     b'check-relroot',
     default=False,
 )
+# Track copy information for all file, not just "added" one (very slow)
+coreconfigitem(
+    b'devel',
+    b'copy-tracing.trace-all-files',
+    default=False,
+)
 coreconfigitem(
     b'devel',
     b'default-date',

mercurial/copies.py

@@ -152,13 +152,21 b' def _committedforwardcopies(a, b, base, '
     if b.p1() == a and b.p2().node() == nullid:
         filesmatcher = matchmod.exact(b.files())
         forwardmissingmatch = matchmod.intersectmatchers(match, filesmatcher)
-    missing = _computeforwardmissing(a, b, match=forwardmissingmatch)
+    if repo.ui.configbool(b'devel', b'copy-tracing.trace-all-files'):
+        missing = list(b.walk(match))
+        # _computeforwardmissing(a, b, match=forwardmissingmatch)
+        if debug:
+            dbg(b'debug.copies:      searching all files: %d\n' % len(missing))
+    else:
+        missing = _computeforwardmissing(a, b, match=forwardmissingmatch)
+        if debug:
+            dbg(
+                b'debug.copies:      missing files to search: %d\n'
+                % len(missing)
+            )
 
     ancestrycontext = a._repo.changelog.ancestors([b.rev()], inclusive=True)
 
-    if debug:
-        dbg(b'debug.copies:      missing files to search: %d\n' % len(missing))
-
     for f in sorted(missing):
         if debug:
             dbg(b'debug.copies:        tracing file: %s\n' % f)

tests/test-copies.t

@@ -95,6 +95,8 b' Copy a file onto another file'
   x -> y
   $ hg debugpathcopies 0 1
   x -> y (no-filelog !)
+  $ hg debugpathcopies 0 1  --config devel.copy-tracing.trace-all-files=yes
+  x -> y
 
 Copy a file onto another file with same content. If metadata is stored in changeset, this does not
 produce a new filelog entry. The changeset's "files" entry should still list the file.
@@ -113,6 +115,8 b' produce a new filelog entry. The changes'
   x -> x2
   $ hg debugpathcopies 0 1
   x -> x2 (no-filelog !)
+  $ hg debugpathcopies 0 1  --config devel.copy-tracing.trace-all-files=yes
+  x -> x2
 
 Rename file in a loop: x->y->z->x
   $ newrepo

tests/test-copy.t

@@ -228,6 +228,17 b' should match'
 should show no copies
   $ hg st -C
 
+note: since filelog based copy tracing only trace copy for new file, the copy information here is not displayed.
+
+  $ hg status --copies --change .
+  M bar
+
+They are a devel option to walk all file and fine this information anyway.
+
+  $ hg status --copies --change . --config devel.copy-tracing.trace-all-files=yes
+  M bar
+    foo
+
 copy --after on an added file
   $ cp bar baz
   $ hg add baz