diff: update synopsis to use --from/--to instead of -r

Differential Revision: https://phab.mercurial-scm.org/D9563

mercurial/commands.py

@@ -2456,15 +2456,15 b" def debugcomplete(ui, cmd=b'', **opts):"
     b'diff',
     [
         (b'r', b'rev', [], _(b'revision'), _(b'REV')),
-        (b'', b'from', b'', _(b'revision to diff from'), _(b'REV')),
-        (b'', b'to', b'', _(b'revision to diff to'), _(b'REV')),
+        (b'', b'from', b'', _(b'revision to diff from'), _(b'REV1')),
+        (b'', b'to', b'', _(b'revision to diff to'), _(b'REV2')),
         (b'c', b'change', b'', _(b'change made by revision'), _(b'REV')),
     ]
     + diffopts
     + diffopts2
     + walkopts
     + subrepoopts,
-    _(b'[OPTION]... ([-c REV] | [-r REV1 [-r REV2]]) [FILE]...'),
+    _(b'[OPTION]... ([-c REV] | [--from REV1] [--to REV2]) [FILE]...'),
     helpcategory=command.CATEGORY_FILE_CONTENTS,
     helpbasic=True,
     inferrepo=True,

tests/test-help.t

@@ -629,7 +629,7 b' Test command without options'
   (some details hidden, use --verbose to show complete help)
 
   $ hg help diff
-  hg diff [OPTION]... ([-c REV] | [-r REV1 [-r REV2]]) [FILE]...
+  hg diff [OPTION]... ([-c REV] | [--from REV1] [--to REV2]) [FILE]...
   
   diff repository (or selected files)
   
@@ -666,8 +666,8 b' Test command without options'
   options ([+] can be repeated):
   
    -r --rev REV [+]         revision
-      --from REV            revision to diff from
-      --to REV              revision to diff to
+      --from REV1           revision to diff from
+      --to REV2             revision to diff to
    -c --change REV          change made by revision
    -a --text                treat all files as text
    -g --git                 use git extended diff format