templates: add built-in files() function

templates: add built-in files() function

We already support multiple primitive for listing files, which were
affected by the current changeset.
This patch adds files() which returns files of the current changeset
matching a given pattern or fileset query via the "set:" prefix.

--- a/mercurial/help/templates.txt	Sat Sep 17 17:02:56 2016 +1000
+++ b/mercurial/help/templates.txt	Fri Sep 23 08:15:05 2016 +0000
@@ -95,6 +95,10 @@
 
    $ hg log -r 0 --template "files: {join(files, ', ')}\n"
 
+- Join the list of files ending with ".py" with a ", "::
+
+   $ hg log -r 0 --template "pythonfiles: {join(files('**.py'), ', ')}\n"
+
 - Separate non-empty arguments by a " "::
 
    $ hg log -r 0 --template "{separate(' ', node, bookmarks, tags}\n"

--- a/mercurial/templater.py	Sat Sep 17 17:02:56 2016 +1000
+++ b/mercurial/templater.py	Fri Sep 23 08:15:05 2016 +0000
@@ -480,6 +480,20 @@
 
     return ''.join(chunks)
 
+@templatefunc('files(pattern)')
+def files(context, mapping, args):
+    """All files of the current changeset matching the pattern. See
+    :hg:`help patterns`."""
+    if not len(args) == 1:
+        # i18n: "files" is a keyword
+        raise error.ParseError(_("files expects one argument"))
+
+    raw = evalstring(context, mapping, args[0])
+    ctx = mapping['ctx']
+    m = ctx.match([raw])
+    files = list(ctx.matches(m))
+    return templatekw.showlist("file", files, **mapping)
+
 @templatefunc('fill(text[, width[, initialident[, hangindent]]])')
 def fill(context, mapping, args):
     """Fill many

--- a/tests/test-command-template.t	Sat Sep 17 17:02:56 2016 +1000
+++ b/tests/test-command-template.t	Fri Sep 23 08:15:05 2016 +0000
@@ -3501,6 +3501,26 @@
   5:13207e5a10d9fd28ec424934298e176197f2c67f,
   4:bbe44766e73d5f11ed2177f1838de10c53ef3e74
 
+Test files function
+
+  $ hg log -T "{rev}\n{join(files('*'), '\n')}\n"
+  2
+  a
+  aa
+  b
+  1
+  a
+  0
+  a
+
+  $ hg log -T "{rev}\n{join(files('aa'), '\n')}\n"
+  2
+  aa
+  1
+  
+  0
+  
+
 Test active bookmark templating
 
   $ hg book foo

--- a/tests/test-help.t	Sat Sep 17 17:02:56 2016 +1000
+++ b/tests/test-help.t	Fri Sep 23 08:15:05 2016 +0000
@@ -1551,6 +1551,9 @@
   $ hg help template.files
       files         List of strings. All files modified, added, or removed by
                     this changeset.
+      files(pattern)
+                    All files of the current changeset matching the pattern. See
+                    'hg help patterns'.
 
 Test section lookup by translated message