mq: qpop should act like quilt pop

qpop patchname would pop the named patch off the stack.  This is slightly
different from how quilt pop works.  quilt pop pops everything up to the
named patch.

hgext/mq.py

@@ -708,7 +708,8 b' class queue:'
             self.ui.write("Now at: %s\n" % top)
         return ret[0]
 
-    def pop(self, repo, patch=None, force=False, update=True, wlock=None):
+    def pop(self, repo, patch=None, force=False, update=True, all=False,
+            wlock=None):
         def getfile(f, rev):
             t = repo.file(f).read(rev)
             try:
@@ -749,7 +750,17 b' class queue:'
         self.applied_dirty = 1;
         end = len(self.applied)
         if not patch:
-            info = [len(self.applied) - 1] + self.applied[-1].split(':')
+            if all:
+                popi = 0
+            else:
+                popi = len(self.applied) - 1
+        else:
+            popi = info[0] + 1
+            if popi >= end:
+                self.ui.warn("qpop: %s is already at the top\n" % patch)
+                return
+        info = [ popi ] + self.applied[popi].split(':')
+
         start = info[0]
         rev = revlog.bin(info[1])
 
@@ -1276,9 +1287,7 b' def pop(ui, repo, patch=None, **opts):'
         localupdate = False
     else:
         q = repomap[repo]
-    if opts['all'] and len(q.applied) > 0:
-        patch = q.applied[0].split(':')[1]
-    q.pop(repo, patch, force=opts['force'], update=localupdate)
+    q.pop(repo, patch, force=opts['force'], update=localupdate, all=opts['all'])
     q.save_dirty()
     return 0