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.

Makefile

@@ -234,7 +234,7 @@ LIB_FILE=libgit.a
 XDIFF_LIB=xdiff/lib.a
 
 LIB_H = \
-	archive.h blob.h cache.h commit.h csum-file.h delta.h \
+	archive.h blob.h cache.h commit.h csum-file.h delta.h grep.h \
 	diff.h object.h pack.h pkt-line.h quote.h refs.h list-objects.h sideband.h \
 	run-command.h strbuf.h tag.h tree.h git-compat-util.h revision.h \
 	tree-walk.h log-tree.h dir.h path-list.h unpack-trees.h builtin.h
@@ -254,7 +254,7 @@ LIB_OBJS = \
 	server-info.o setup.o sha1_file.o sha1_name.o strbuf.o \
 	tag.o tree.o usage.o config.o environment.o ctype.o copy.o \
 	fetch-clone.o revision.o pager.o tree-walk.o xdiff-interface.o \
-	write_or_die.o trace.o list-objects.o \
+	write_or_die.o trace.o list-objects.o grep.o \
 	alloc.o merge-file.o path-list.o help.o unpack-trees.o $(DIFF_OBJS) \
 	color.o wt-status.o archive-zip.o