[PATCH] revset: introduce the summary predicate

[Matt Harbison]

# HG changeset patch
# User Matt Harbison <matt_harbison at yahoo.com>
# Date 1483550016 18000
#      Wed Jan 04 12:13:36 2017 -0500
# Node ID 76d95ab94b9e206363629059fb7824002e19a9e5
# Parent  0064a1eb28e246ded9b726c696d048143d1b23f1
revset: introduce the summary predicate

This is similar to the 'desc()' predicate, however the search is limited to the
first line, which I couldn't figure out how to do with the existing
functionality.  Unlike 'desc()', this supports regular expressions.  The
'matching()' revset already treats the summary line distinctly from the full
description, but that finds similar revisions instead of searching with a
string.

I'm torn on whether it should support case insensitivity, like 'desc()' and
'keyword()'.  It can be handy, but it seems like it would be surprising if
literals and regex are handled differently, or if the regex was adjusted to be
case insensitive internally.

The use case is to be able to select bug fixes out of the summary line, while
ignoring similar markers within the body of the commit.  I've seen previously
where the bug bot will erroneously update a bug that is mentioned as a
parenthetical within the detail of the commit message.  To illustrate on the
local Mercurial repo (some old markers have an internal space):

  $ hg log -r "desc(r' (issue')" -T "{rev}\n" | wc -l
  1672
  $ hg log -r "desc(r' (issue')" -T "{desc|firstline}\n"  \
  >            | egrep '\(issue' | wc -l
  1633
  $ hg log -r "desc(r' (issue')" -T "{desc|firstline}\n"  \
  >            | egrep '\(issue[0-9]+\)' | wc -l
  1560
  $ hg log -r "summary(r're: \(issue\d+\)')" -T "{rev}\n" | wc -l
  1560

I'm not sure why the splitlines() logic is that complicated, but I copy/pasted
from templatefilters.firstline() for consistency.

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -2197,6 +2197,32 @@ def subrepo(repo, subset, x):
 
     return subset.filter(matches, condrepr=('<subrepo %r>', pat))
 
+ at predicate('summary(string)', safe=True)
+def summary(repo, subset, x):
+    """Changesets with the given string in the summary line.  The match is case
+    sensitive.
+
+    If `value` starts with `re:`, the remainder of the value is treated as
+    a regular expression. To match a value that actually starts with `re:`,
+    use the prefix `literal:`.
+    """
+
+    # i18n: "summary" is a keyword
+    s = getstring(x, _("summary requires a string"))
+    kind, value, matcher = _substringmatcher(s)
+
+    def _matchvalue(r):
+        _desc = repo[r].description()
+        _sum = ''
+        try:
+            _sum = _desc.splitlines(True)[0].rstrip('\r\n')
+        except IndexError:
+            pass
+
+        return matcher(_sum)
+
+    return subset.filter(lambda r: _matchvalue(r), condrepr=('<summary %r>', s))
+
 def _substringmatcher(pattern):
     kind, pattern, matcher = util.stringmatcher(pattern)
     if kind == 'literal':
diff --git a/tests/test-commit.t b/tests/test-commit.t
--- a/tests/test-commit.t
+++ b/tests/test-commit.t
@@ -252,13 +252,50 @@ full log
   commit-foo-subdir
   
   
+  $ cat > ../commit-log-test <<EOF
+  > issue fix (bug1234)
+  > 
+  > multiline description here
+  > EOF
+  $ echo "edited" >> foo/plain-file
+  $ hg ci -l ../commit-log-test
+
+Summary doesn't search past the first line
+  $ hg log -r "summary('description')"
+
+Summary works with regex
+  $ hg log -r "summary(r're:\(bug\d+\)')"
+  changeset:   2:5364ddbe8265
+  tag:         tip
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     issue fix (bug1234)
+  
+
+Summary works with partial matches
+  $ hg log -r "summary('foo')"
+  changeset:   0:65d4e9386227
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     commit-foo-subdir
+  
+  changeset:   1:95b38e3a5b2e
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     commit-foo-dot
+  
 
 subdir log
 
   $ cd foo
   $ hg log .
+  changeset:   2:5364ddbe8265
+  tag:         tip
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     issue fix (bug1234)
+  
   changeset:   1:95b38e3a5b2e
-  tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     commit-foo-dot