largefiles: show hashes before prompting for conflict resolution

The largefile hashes are mostly an implementation detail, but they are "leaked"
in several places anyway, and showing the hashes is better than not giving the
user any information about the options in the prompt.

The hashes are long, but it is largefile hashes and it would thus be confusing
to shorten them.

hgext/largefiles/overrides.py

@@ -426,10 +426,13 b' def overridefilemerge(origfn, repo, myno'
         if not fcother.cmp(fcdest): # files identical?
             return None
 
-        if repo.ui.promptchoice(_('largefile %s has a merge conflict\n'
-                                  'keep (l)ocal or take (o)ther?'
-                                  '$$ &Local $$ &Other') %
-                                lfutil.splitstandin(orig), 0) == 0:
+        if repo.ui.promptchoice(
+            _('largefile %s has a merge conflict\nancestor was %s\n'
+              'keep (l)ocal %s or\ntake (o)ther %s?'
+              '$$ &Local $$ &Other') %
+              (lfutil.splitstandin(orig),
+               fca.data().strip(), fcd.data().strip(), fco.data().strip()),
+            0) == 0:
             return 0
         else:
             repo.wwrite(fcdest.path(), fcother.data(), fcother.flags())

tests/test-largefiles.t

@@ -1375,7 +1375,9 b' correctly.'
   2 largefiles cached
   $ hg merge
   largefile sub/large4 has a merge conflict
-  keep (l)ocal or take (o)ther? l
+  ancestor was 971fb41e78fea4f8e0ba5244784239371cb00591
+  keep (l)ocal d846f26643bfa8ec210be40cc93cc6b7ff1128ea or
+  take (o)ther e166e74c7303192238d60af5a9c4ce9bef0b7928? l
   3 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   getting changed largefiles