revpair: smartset compatibility

Since recent revset changes, revrange now return a smartset. This smart set
probably does not support indexing (_addset does not). This led to crash.
Instead when the smartset is ordered we use the `min` and `max` method of
smart set. Otherwise we turn is into a list and use indexing on it.

The tests have been updated to catch such regression.

mercurial/scmutil.py

@@ -470,13 +470,26 b' def revpair(repo, revs):'
 
     l = revrange(repo, revs)
 
-    if len(l) == 0:
+    if not l:
+        first = second = None
+    elif l.isascending():
+        first = l.min()
+        second = l.max()
+    elif l.isdescending():
+        first = l.max()
+        second = l.min()
+    else:
+        l = list(l)
+        first = l[0]
+        second = l[-1]
+
+    if first is None:
         raise util.Abort(_('empty revision range'))
 
-    if len(l) == 1 and len(revs) == 1 and _revrangesep not in revs[0]:
-        return repo.lookup(l[0]), None
+    if first == second and len(revs) == 1 and _revrangesep not in revs[0]:
+        return repo.lookup(first), None
 
-    return repo.lookup(l[0]), repo.lookup(l[-1])
+    return repo.lookup(first), repo.lookup(second)
 
 _revrangesep = ':'
 

tests/test-revset.t

@@ -744,6 +744,43 b' multiple revspecs'
   6
   7
 
+test usage in revpair (with "+")
+
+(real pair)
+
+  $ hg diff -r 'tip^^' -r 'tip'
+  diff -r 2326846efdab -r 24286f4ae135 .hgtags
+  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+  +++ b/.hgtags	Thu Jan 01 00:00:00 1970 +0000
+  @@ -0,0 +1,1 @@
+  +e0cc66ef77e8b6f711815af4e001a6594fde3ba5 1.0
+  $ hg diff -r 'tip^^::tip'
+  diff -r 2326846efdab -r 24286f4ae135 .hgtags
+  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+  +++ b/.hgtags	Thu Jan 01 00:00:00 1970 +0000
+  @@ -0,0 +1,1 @@
+  +e0cc66ef77e8b6f711815af4e001a6594fde3ba5 1.0
+
+(single rev)
+
+  $ hg diff -r 'tip^' -r 'tip^'
+  $ hg diff -r 'tip^::tip^ or tip^'
+
+(single rev that does not looks like a range)
+
+  $ hg diff -r 'tip^ or tip^'
+  diff -r d5d0dcbdc4d9 .hgtags
+  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+  +++ b/.hgtags	* (glob)
+  @@ -0,0 +1,1 @@
+  +e0cc66ef77e8b6f711815af4e001a6594fde3ba5 1.0
+
+(no rev)
+
+  $ hg diff -r 'author("babar") or author("celeste")'
+  abort: empty revision range
+  [255]
+
 aliases:
 
   $ echo '[revsetalias]' >> .hg/hgrc