blame: Document and add help text for -f, -n, and -p

New options --show-name, --show-number and --porcelain were not
documented.  Also add -p as a short-hand for --porcelain for
consistency.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-blame.txt

@@ -7,7 +7,7 @@ git-blame - Show what revision and author last modified each line of a file
 
 SYNOPSIS
 --------
-'git-blame' [-c] [-l] [-t] [-S <revs-file>] [--] <file> [<rev>]
+'git-blame' [-c] [-l] [-t] [-f] [-n] [-p] [-S <revs-file>] [--] <file> [<rev>]
 
 DESCRIPTION
 -----------
@@ -45,10 +45,47 @@ OPTIONS
 -S, --rev-file <revs-file>::
 	Use revs from revs-file instead of calling gitlink:git-rev-list[1].
 
+-f, --show-name::
+	Show filename in the original commit.  By default
+	filename is shown if there is any line that came from a
+	file with different name, due to rename detection.
+
+-n, --show-number::
+	Show line number in the original commit (Default: off).
+
+-p, --porcelain::
+	Show in a format designed for machine consumption.
+
 -h, --help::
 	Show help message.
 
 
+THE PORCELAIN FORMAT
+--------------------
+
+In this format, each line is output after a header; the
+header at the minumum has the first line which has:
+
+- 40-byte SHA-1 of the commit the line is attributed to;
+- the line number of the line in the original file;
+- the line number of the line in the final file;
+- on a line that starts a group of line from a different
+  commit than the previous one, the number of lines in this
+  group.  On subsequent lines this field is absent.
+
+This header line is followed by the following information
+at least once for each commit:
+
+- author name ("author"), email ("author-mail"), time
+  ("author-time"), and timezone ("author-tz"); similarly
+  for committer.
+- filename in the commit the line is attributed to.
+- the first line of the commit log message ("summary").
+
+The contents of the actual line is output after the above
+header, prefixed by a TAB. This is to allow adding more
+header elements later.
+
 SEE ALSO
 --------
 gitlink:git-annotate[1]

blame.c

@@ -22,11 +22,14 @@
 #define DEBUG 0
 
 static const char blame_usage[] =
-"git-blame [-c] [-l] [-t] [-S <revs-file>] [--] file [commit]\n"
+"git-blame [-c] [-l] [-t] [-f] [-n] [-p] [-S <revs-file>] [--] file [commit]\n"
 "  -c, --compatibility Use the same output mode as git-annotate (Default: off)\n"
 "  -l, --long          Show long commit SHA1 (Default: off)\n"
 "  -t, --time          Show raw timestamp (Default: off)\n"
-"  -S, --revs-file     Use revisions from revs-file instead of calling git-rev-list\n"
+"  -f, --show-name     Show original filename (Default: auto)\n"
+"  -n, --show-number   Show original linenumber (Default: off)\n"
+"  -p, --porcelain     Show in a format designed for machine consumption\n"
+"  -S revs-file        Use revisions from revs-file instead of calling git-rev-list\n"
 "  -h, --help          This message";
 
 static struct commit **blame_lines;
@@ -951,7 +954,8 @@ int main(int argc, const char **argv)
 				show_number = 1;
 				continue;
 			}
-			if (!strcmp(argv[i], "--porcelain")) {
+			if (!strcmp(argv[i], "-p") ||
+			    !strcmp(argv[i], "--porcelain")) {
 				porcelain = 1;
 				sha1_len = 40;
 				show_raw_time = 1;