hooks: prioritize run order of hooks

As of Mercurial 1.3, hooks are sorted in the order they are read into
Mercurial.  There are many instances when someone may want the hooks
sorted in a specific order; this patch allows prioritizing hooks, while
maintaining the existing enumeration for hooks without a priority.

mercurial/help/config.txt

@@ -655,7 +655,10 b' Commands or Python functions that get au'
 various actions such as starting or finishing a commit. Multiple
 hooks can be run for the same action by appending a suffix to the
 action. Overriding a site-wide hook can be done by changing its
-value or setting it to an empty string.
+value or setting it to an empty string.  Hooks can be prioritized
+by adding a prefix of ``priority`` to the hook name on a new line
+and setting the priority.  The default priority is 0 if
+not specified.
 
 Example ``.hg/hgrc``::
 
@@ -666,6 +669,8 b' Example ``.hg/hgrc``::'
   incoming =
   incoming.email = /my/email/hook
   incoming.autobuild = /my/build/hook
+  # force autobuild hook to run before other incoming hooks
+  priority.incoming.autobuild = 1
 
 Most hooks are run with environment variables set that give useful
 additional information. For each hook below, the environment

mercurial/hook.py

@@ -124,6 +124,14 b' def _exthook(ui, repo, name, cmd, args, '
         ui.warn(_('warning: %s hook %s\n') % (name, desc))
     return r
 
+def _allhooks(ui):
+    hooks = []
+    for name, cmd in ui.configitems('hooks'):
+        if not name.startswith('priority'):
+            priority = ui.configint('hooks', 'priority.%s' % name, 0)
+            hooks.append((-priority, len(hooks), name, cmd))
+    return [(k, v) for p, o, k, v in sorted(hooks)]
+
 _redirect = False
 def redirect(state):
     global _redirect
@@ -147,7 +155,7 b' def hook(ui, repo, name, throw=False, **'
             pass
 
     try:
-        for hname, cmd in ui.configitems('hooks'):
+        for hname, cmd in _allhooks(ui):
             if hname.split('.')[0] != name or not cmd:
                 continue
             if util.safehasattr(cmd, '__call__'):

tests/test-hook.t

@@ -553,3 +553,19 b' that is passed to pre/post hooks'
   calling hook pre-identify: hooktests.verbosehook
   verbose output from hook
   cb9a9f314b8b
+
+Ensure hooks can be prioritized
+
+  $ echo '[hooks]' > .hg/hgrc
+  $ echo 'pre-identify.a = python:hooktests.verbosehook' >> .hg/hgrc
+  $ echo 'pre-identify.b = python:hooktests.verbosehook' >> .hg/hgrc
+  $ echo 'priority.pre-identify.b = 1' >> .hg/hgrc
+  $ echo 'pre-identify.c = python:hooktests.verbosehook' >> .hg/hgrc
+  $ hg id --verbose
+  calling hook pre-identify.b: hooktests.verbosehook
+  verbose output from hook
+  calling hook pre-identify.a: hooktests.verbosehook
+  verbose output from hook
+  calling hook pre-identify.c: hooktests.verbosehook
+  verbose output from hook
+  cb9a9f314b8b