[PATCH 2 of 2] template: add pad function for padding output

[Durham Goode]

# HG changeset patch
# User Durham Goode <durham at fb.com>
# Date 1389946608 28800
#      Fri Jan 17 00:16:48 2014 -0800
# Node ID 77cf62dd2af0b5631a2864744e720e61ad4cde6a
# Parent  b18359a70b640d2aeb3f4afd1c8e47d775402b8e
template: add pad function for padding output

Adds a pad template function with the following signature:

pad(text, width, right=False, fillchar=' ')

This uses the standard python ljust and rjust functions to produce a string
that is at least a certain width. This is especially useful with the
introduction of a '{shortestnode}' keyword, since the output can be variable
length.

diff --git a/mercurial/templater.py b/mercurial/templater.py
--- a/mercurial/templater.py
+++ b/mercurial/templater.py
@@ -245,6 +245,31 @@
 
     return templatefilters.fill(text, width, initindent, hangindent)
 
+def pad(context, mapping, args):
+    """usage: pad(text, width, right=False, fillchar=' ')
+    """
+    if not (2 <= len(args) <= 4):
+        raise error.ParseError(_("pad() expects two to four arguments"))
+
+    width = int(stringify(args[1][0](context, mapping, args[1][1])))
+
+    text = stringify(args[0][0](context, mapping, args[0][1]))
+    if args[0][0] == runstring:
+        text = stringify(runtemplate(context, mapping,
+            compiletemplate(text, context)))
+
+    right = False
+    fillchar = ' '
+    if len(args) > 2:
+        right = stringify(args[2][0](context, mapping, args[2][1])) == "True"
+    if len(args) > 3:
+        fillchar = stringify(args[3][0](context, mapping, args[3][1]))
+
+    if right:
+        return text.rjust(width, fillchar)
+    else:
+        return text.ljust(width, fillchar)
+
 def get(context, mapping, args):
     if len(args) != 2:
         # i18n: "get" is a keyword
@@ -368,6 +393,7 @@
     "ifeq": ifeq,
     "join": join,
     "label": label,
+    "pad": pad,
     "rstdoc": rstdoc,
     "strip": strip,
     "sub": sub,
diff --git a/tests/test-command-template.t b/tests/test-command-template.t
--- a/tests/test-command-template.t
+++ b/tests/test-command-template.t
@@ -1635,3 +1635,16 @@
   d97c
   f776
 
+Test pad function
+
+  $ hg log --template '{pad("{shortestnode}", "20")} {author|user}\n'
+  d97c                 test
+  f776                 test
+
+  $ hg log --template '{pad("{shortestnode}", "20", "True")} {author|user}\n'
+                  d97c test
+                  f776 test
+
+  $ hg log --template '{pad("{shortestnode}", "20", "False", "-")} {author|user}\n'
+  d97c---------------- test
+  f776---------------- test