dispatch: add shell aliases

This patch adds git-style "shell aliases" to Mercurial.

Any alias with a definition beginning with a '!' will be treated as a shell
alias. For example:

    [alias]
    echo = !echo
    qempty = !hg qrefresh -X "`hg root`" ; echo Emptied patch "`hg qtop`"

    $ hg echo foo
    foo
    $ hg qempty
    Emptied patch foo
    $

mercurial/commands.py

@@ -1866,7 +1866,10 b' def help_(ui, name=None, with_version=Fa'
         if not doc:
             doc = _("(no help text available)")
         if hasattr(entry[0], 'definition'):  # aliased command
-            doc = _('alias for: hg %s\n\n%s') % (entry[0].definition, doc)
+            if entry[0].definition.startswith('!'):  # shell alias
+                doc = _('shell alias for::\n\n    %s') % entry[0].definition[1:]
+            else:
+                doc = _('alias for: hg %s\n\n%s') % (entry[0].definition, doc)
         if ui.quiet:
             doc = doc.splitlines()[0]
         keep = ui.verbose and ['verbose'] or []

mercurial/dispatch.py

@@ -208,6 +208,13 b' class cmdalias(object):'
 
             return
 
+        if self.definition.startswith('!'):
+            def fn(ui, *args):
+                cmd = '%s %s' % (self.definition[1:], ' '.join(args))
+                return util.system(cmd)
+            self.fn = fn
+            return
+
         args = shlex.split(self.definition)
         cmd = args.pop(0)
         args = map(util.expandpath, args)

tests/test-alias

@@ -14,6 +14,7 b" shortlog = log --template '{rev} {node|s"
 dln = lognull --debug
 nousage = rollback
 put = export -r 0 -o "\$FOO/%R.diff"
+echo = !echo
 
 [defaults]
 mylog = -q
@@ -64,3 +65,6 b' hg dln'
 echo '% path expanding'
 FOO=`pwd` hg put
 cat 0.diff
+
+echo '% shell aliases'
+hg echo foo

tests/test-alias.out

@@ -43,3 +43,5 b' diff -r 000000000000 -r e63c23eaa88a foo'
 +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
 @@ -0,0 +1,1 @@
 +foo
+% shell aliases
+foo