templater: switch ctx of list expression to rev of revset() (BC)

Because revset() function generates a list of revisions, it seems sensible
to switch the ctx as well where a list expression will be evaluated. I think
"{revset(...) % "..."}" expression wasn't considered well when it was
introduced at cda9d2b6beab.

mercurial/help/templates.txt

@@ -106,6 +106,10 b' Some sample command line templates:'
 
    $ hg log --template "{ifcontains(rev, revset('.'), '@')}\n"
 
+- Show details of parent revisions::
+
+   $ hg log --template "{revset('parents(%d)', rev) % '{desc|firstline}\n'}"
+
 - Show only commit descriptions that start with "template"::
 
    $ hg log --template "{startswith('template', firstline(desc))}\n"

mercurial/templatekw.py

@@ -409,6 +409,14 b' def showrev(repo, ctx, templ, **args):'
     """:rev: Integer. The repository-local changeset revision number."""
     return scmutil.intrev(ctx.rev())
 
+def showrevslist(name, revs, **args):
+    """helper to generate a list of revisions in which a mapped template will
+    be evaluated"""
+    repo = args['ctx'].repo()
+    f = _showlist(name, revs, **args)
+    return _hybrid(f, revs,
+                   lambda x: {name: x, 'ctx': repo[x], 'revcache': {}})
+
 def showsubrepos(**args):
     """:subrepos: List of strings. Updated subrepositories in the changeset."""
     ctx = args['ctx']

mercurial/templater.py

@@ -568,7 +568,7 b' def revset(context, mapping, args):'
             revs = list([str(r) for r in revs])
             revsetcache[raw] = revs
 
-    return templatekw.showlist("revision", revs, **mapping)
+    return templatekw.showrevslist("revision", revs, **mapping)
 
 def rstdoc(context, mapping, args):
     """:rstdoc(text, style): Format ReStructuredText."""

tests/test-command-template.t

@@ -3234,6 +3234,23 b' Test revset function'
   $ hg log --template '{revset("TIP"|lower)}\n' -l1
   2
 
+ a list template is evaluated for each item of revset
+
+  $ hg log -T '{rev} p: {revset("p1(%s)", rev) % "{rev}:{node|short}"}\n'
+  2 p: 1:bcc7ff960b8e
+  1 p: 0:f7769ec2ab97
+  0 p: 
+
+ therefore, 'revcache' should be recreated for each rev
+
+  $ hg log -T '{rev} {file_adds}\np {revset("p1(%s)", rev) % "{file_adds}"}\n'
+  2 aa b
+  p 
+  1 
+  p a
+  0 a
+  p 
+
 Test active bookmark templating
 
   $ hg book foo