help: fix help argument parsing and documentation

help: fix help argument parsing and documentation

support combining -c and -e

previously -k was misdocumented:
 * the first line didn't mention it
 * the help half implied you could do help -k keyword topic

with these changes, -k just changes the search method

support -c and -e for -k searches

--- a/mercurial/commands.py	Thu Sep 10 10:48:20 2015 -0400
+++ b/mercurial/commands.py	Thu Sep 10 20:22:37 2015 -0400
@@ -3942,9 +3942,9 @@
 @command('help',
     [('e', 'extension', None, _('show only help for extensions')),
      ('c', 'command', None, _('show only help for commands')),
-     ('k', 'keyword', '', _('show topics matching keyword')),
+     ('k', 'keyword', None, _('show topics matching keyword')),
      ],
-    _('[-ec] [TOPIC]'),
+    _('[-eck] [TOPIC]'),
     norepo=True)
 def help_(ui, name=None, **opts):
     """show help for a given topic or a help overview

--- a/mercurial/help.py	Thu Sep 10 10:48:20 2015 -0400
+++ b/mercurial/help.py	Thu Sep 10 20:22:37 2015 -0400
@@ -475,11 +475,18 @@
     rst = []
     kw = opts.get('keyword')
     if kw:
-        matches = topicmatch(kw)
-        for t, title in (('topics', _('Topics')),
+        matches = topicmatch(name)
+        helpareas = []
+        if opts.get('extension'):
+            helpareas += [('extensions', _('Extensions'))]
+        if opts.get('command'):
+            helpareas += [('commands', _('Commands'))]
+        if not helpareas:
+            helpareas = [('topics', _('Topics')),
                          ('commands', _('Commands')),
                          ('extensions', _('Extensions')),
-                         ('extensioncommands', _('Extension Commands'))):
+                         ('extensioncommands', _('Extension Commands'))]
+        for t, title in helpareas:
             if matches[t]:
                 rst.append('%s:\n\n' % title)
                 rst.extend(minirst.maketable(sorted(matches[t]), 1))
@@ -489,13 +496,14 @@
             hint = _('try "hg help" for a list of topics')
             raise util.Abort(msg, hint=hint)
     elif name and name != 'shortlist':
+        queries = []
         if unknowncmd:
-            queries = (helpextcmd,)
-        elif opts.get('extension'):
-            queries = (helpext,)
-        elif opts.get('command'):
-            queries = (helpcmd,)
-        else:
+            queries += [helpextcmd]
+        if opts.get('extension'):
+            queries += [helpext]
+        if opts.get('command'):
+            queries += [helpcmd]
+        if not queries:
             queries = (helptopic, helpcmd, helpext, helpextcmd)
         for f in queries:
             try:

--- a/tests/test-help.t	Thu Sep 10 10:48:20 2015 -0400
+++ b/tests/test-help.t	Thu Sep 10 20:22:37 2015 -0400
@@ -988,6 +988,28 @@
       helphook1
       helphook2
 
+Test -e / -c / -k combinations
+
+  $ hg help -c progress
+  abort: no such help topic: progress
+  (try "hg help --keyword progress")
+  [255]
+  $ hg help -e progress |head -1
+  progress extension - show progress bars for some actions (DEPRECATED)
+  $ hg help -c -k dates |egrep '^(Topics|Extensions|Commands):'
+  Commands:
+  $ hg help -e -k a |egrep '^(Topics|Extensions|Commands):'
+  Extensions:
+  $ hg help -e -c -k date |egrep '^(Topics|Extensions|Commands):'
+  Extensions:
+  Commands:
+  $ hg help -c commit > /dev/null
+  $ hg help -e -c commit > /dev/null
+  $ hg help -e commit > /dev/null
+  abort: no such help topic: commit
+  (try "hg help --keyword commit")
+  [255]
+
 Test keyword search help
 
   $ cat > prefixedname.py <<EOF