merge: use labels in prompts to the user Now that we persist the labels, we can consistently use the labels in prompts for the user without risk of confusion. This changes a huge amount of command output: This means that merge prompts like: no tool found to merge a keep (l)ocal, take (o)ther, or leave (u)nresolved? u and remote changed a which local deleted use (c)hanged version, leave (d)eleted, or leave (u)nresolved? c become: no tool found to merge a keep (l)ocal [working copy], take (o)ther [destination], or leave (u)nresolved? u and remote [source] changed a which local [dest] deleted use (c)hanged version, leave (d)eleted, or leave (u)nresolved? c where "working copy" and "destination" were supplied by the command that requested the merge as labels for conflict markers, and thus should be human-friendly.

--- a/tests/test-merge-types.t	Tue Aug 09 09:15:46 2016 -0700
+++ b/tests/test-merge-types.t	Fri Aug 12 06:01:42 2016 -0700
@@ -173,7 +173,7 @@
   (couldn't find merge tool hgmerge|tool hgmerge can't handle symlinks) (re)
   picked tool ':prompt' for a (binary False symlink True changedelete False)
   no tool found to merge a
-  keep (l)ocal, take (o)ther, or leave (u)nresolved? u
+  keep (l)ocal [working copy], take (o)ther [destination], or leave (u)nresolved? u
   0 files updated, 0 files merged, 0 files removed, 1 files unresolved
   use 'hg resolve' to retry unresolved file merges
   1 other heads for branch "default"