templatefuncs: add truncate parameter to pad

templatefuncs: add truncate parameter to pad

Add a truncate option to pad that additionally truncates the text to the pad
width if it is wider.

Since color codes can cause a problem with this, when the text is truncated,
the color codes are also stripped.  Users of the truncate option should label
the text outside the pad.

Differential Revision: https://phab.mercurial-scm.org/D5000

--- a/mercurial/templatefuncs.py	Fri Oct 12 15:46:51 2018 +0000
+++ b/mercurial/templatefuncs.py	Fri Oct 12 15:46:52 2018 +0000
@@ -216,8 +216,9 @@
 
     return stringutil.mapname(cache['mailmap'], author)
 
-@templatefunc('pad(text, width[, fillchar=\' \'[, left=False]])',
-              argspec='text width fillchar left')
+@templatefunc(
+    'pad(text, width[, fillchar=\' \'[, left=False[, truncate=False]]])',
+    argspec='text width fillchar left truncate')
 def pad(context, mapping, args):
     """Pad text with a
     fill character."""
@@ -231,6 +232,7 @@
 
     text = evalstring(context, mapping, args['text'])
 
+    truncate = False
     left = False
     fillchar = ' '
     if 'fillchar' in args:
@@ -240,8 +242,12 @@
             raise error.ParseError(_("pad() expects a single fill character"))
     if 'left' in args:
         left = evalboolean(context, mapping, args['left'])
+    if 'truncate' in args:
+        truncate = evalboolean(context, mapping, args['truncate'])
 
     fillwidth = width - encoding.colwidth(color.stripeffects(text))
+    if fillwidth < 0 and truncate:
+        return encoding.trim(color.stripeffects(text), width, leftside=left)
     if fillwidth <= 0:
         return text
     if left:

--- a/tests/test-template-functions.t	Fri Oct 12 15:46:51 2018 +0000
+++ b/tests/test-template-functions.t	Fri Oct 12 15:46:52 2018 +0000
@@ -696,6 +696,12 @@
   > '{pad(label(red, "red"), 5, label(cyan, "-"))}\n'
   \x1b[0;31mred\x1b[0m\x1b[0;36m-\x1b[0m\x1b[0;36m-\x1b[0m (esc)
 
+pad() with truncate has to strip color codes, though
+
+  $ hg debugtemplate --color=always \
+  > '{pad(label(red, "scarlet"), 5, truncate=true)}\n'
+  scarl
+
 label should be no-op if color is disabled:
 
   $ hg log --color=never -l 1 --template '{label(red, "text\n")}'
@@ -928,6 +934,15 @@
   1------------------- {node|short}
   0------------------- test
 
+  $ hg log --template '{pad(author, 5, "-", False, True)}\n'
+  test-
+  {node
+  test-
+  $ hg log --template '{pad(author, 5, "-", True, True)}\n'
+  -test
+  hort}
+  -test
+
 Test template string in pad function
 
   $ hg log -r 0 -T '{pad("\{{rev}}", 10)} {author|user}\n'