Merge branch 'jc/filter-commit'

* jc/filter-commit:
  git log: Unify header_filter and message_filter into one.
  Update grep internal for grepping only in head/body
  git-log --author and --committer are not left-anchored by default
  rev-list: fix segfault with --{author,committer,grep}
  revision traversal: --author, --committer, and --grep.
  revision traversal: prepare for commit log match.
  builtin-grep: make pieces of it available as library.

Documentation/git-rev-list.txt

@@ -20,6 +20,7 @@ SYNOPSIS
 	     [ \--stdin ]
 	     [ \--topo-order ]
 	     [ \--parents ]
+	     [ \--(author|committer|grep)=<pattern> ]
 	     [ [\--objects | \--objects-edge] [ \--unpacked ] ]
 	     [ \--pretty | \--header ]
 	     [ \--bisect ]
@@ -154,6 +155,16 @@ limiting may be applied.
 
 	Limit the commits output to specified time range.
 
+--author='pattern', --committer='pattern'::
+
+	Limit the commits output to ones with author/committer
+	header lines that match the specified pattern.
+
+--grep='pattern'::
+
+	Limit the commits output to ones with log message that
+	matches the specified pattern.
+
 --remove-empty::
 
 	Stop when a given path disappears from the tree.