templatekw: display active bookmark more consistently (issue4552) (BC)

Previously, the template keyword '{activebookmark}' would only display the
active bookmark if it was also pointing to the working directory's parent.
Meanwhile, the '{active}' subkeyword of the '{bookmarks}' keyword displays
the active bookmark regardless of whether it also points to the working
directory's parent. This is confusing.

Consider the output of these two templates:

  $ hg log -T '{activebookmark}\n' -r indent

  $ hg log -T '{bookmarks % "{bookmark}"}\n' -r indent
  indent

This is the current behavior that can arise after, eg, a pull moves a bookmark
out from under you. After this patch, the first template will also return the
active bookmark that points to a revision, even if it is not the current
parent of the working directory. A test has been added to show the new behavior.

mercurial/templatekw.py

@@ -230,12 +230,9 b' def showcurrentbookmark(**args):'
 def showactivebookmark(**args):
     """:activetbookmark: String. The active bookmark, if it is
     associated with the changeset"""
-    import bookmarks as bookmarks # to avoid circular import issues
-    repo = args['repo']
-    if bookmarks.isactivewdirparent(repo):
-        active = repo._activebookmark
-        if active in args['ctx'].bookmarks():
-            return active
+    active = args['repo']._activebookmark
+    if active and active in args['ctx'].bookmarks():
+        return active
     return ''
 
 def showdate(repo, ctx, templ, **args):

tests/test-bookmarks-current.t

@@ -193,3 +193,12 b' analogous to hg book -i <active bookmark'
   $ hg up -q .
   $ test -f .hg/bookmarks.current
   [1]
+
+issue 4552 -- simulate a pull moving the active bookmark
+
+  $ hg up -q X
+  $ printf "Z" > .hg/bookmarks.current
+  $ hg log -T '{activebookmark}\n' -r Z
+  Z
+  $ hg log -T '{bookmarks % "{active}\n"}' -r Z
+  Z