0001-git-fast-import-s-X-N-X-substr-mark-2.patch

From: Sam Vilain <sam@vilain.net>
Date: Wed, 28 Nov 2007 01:02:17 +1300
Subject: [PATCH] git-fast-import: s/(X+\:\((N)\)X+)/substr($mark[$2],0,length($1))/

Applied Turing Test for Project Submitters: trying to figure out if
that C code was written by hand or a one-liner written by some
smartass with a fancy pants compile system and C target.  Bonus
points: come up with such a compiler.  Extra bonus points: the
original WAS hand-coded.
---
  Based on an irc conversation.

  21:13 < mugwump> spearce: I want to put a commit ID in a commit
                   message with gfi.  any implementation hints?
  21:18 < spearce> i'd try to do it as late as possible, e.g. right
                   before the strbuf_reset around l.2082.
  21:20 < mugwump> Could make the expansion syntax: d00b1ed00b1ed00b, more X's
                   gives you more sha1
  21:21 < mugwump> and do it in-place
  21:21 < mugwump> has a certain appeal
  21:22 < spearce> right until a commit message talks about using that
                   format to do replacement. :-)
  21:23 < mugwump> heh, true

  ... to be continued ... :)

 fast-import.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 81 insertions(+), 0 deletions(-)

diff --git a/fast-import.c b/fast-import.c
index f93d7d6..d7bd95a 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -2012,6 +2012,86 @@ static struct hash_list *cmd_merge(unsigned int *count)
 	return list;
 }
 
+/*  s/(X+\:\((N)\)X+)/substr($mark[$2],0,length($1))/ */
+enum marks_expand_state_switch {
+	MESS_PRE_X,
+	MESS_X,
+	MESS_COLON,
+	MESS_NUM,
+	MESS_CLOSE_PAREN
+};
+
+void strbuf_expand_marks(struct strbuf *sb) {
+	char *next = sb->buf;
+	char *M1 = sb->buf;
+	int offset = 0;
+	enum marks_expand_state_switch state = 0;
+	uintmax_t mark = 0;
+	struct object_entry* ob = NULL;
+	static const char hex[] = "0123456789abcdef";
+	int nybble = 0;
+
+	while (offset < sb->len) {
+		next++;
+		switch (state) {
+		case MESS_PRE_X:
+			if (*next == 'X') {
+				M1 = next;
+				state = MESS_X;
+			}
+			break;
+		case MESS_X:
+			switch (*next) {
+			default:
+				state = MESS_PRE_X;
+				break;
+			case ':':
+				state = MESS_COLON;
+			case 'X':
+				break;
+			}	
+			break;
+		case MESS_COLON:
+			if (*next == '(') {
+				state = MESS_NUM;
+				mark = 0;
+			}
+			else
+				state = MESS_PRE_X;
+			break;
+		case MESS_NUM:
+			if ( (*next <= '9') && (*next >= '0') ) {
+				mark = mark * 10;
+				mark += (*next) - '0';
+				state = MESS_NUM;
+			}
+			else if (*next == ')') {
+				state = (mark ? MESS_CLOSE_PAREN : MESS_PRE_X);
+				nybble = 0;
+			}
+			else {
+				state = MESS_PRE_X;
+			}
+			break;
+		case MESS_CLOSE_PAREN:
+			if (*next != 'X') {
+				state = MESS_PRE_X;
+				break;
+			}
+			if (!nybble) {
+				ob = find_mark(mark);
+			}
+			while (M1 <= next) {
+				unsigned char b = ob->sha1[nybble>>1];
+				*M1 = hex[ (nybble&1) ? (b&0xf) : (b>>4)  ];
+				M1++;
+				nybble++;
+			}
+		}
+		offset++;
+	}
+}
+
 static void cmd_new_commit(void)
 {
 	static struct strbuf msg = STRBUF_INIT;
@@ -2092,6 +2172,7 @@ static void cmd_new_commit(void)
 		"committer %s\n"
 		"\n",
 		author ? author : committer, committer);
+	strbuf_expand_marks(&msg);
 	strbuf_addbuf(&new_data, &msg);
 	free(author);
 	free(committer);
-- 
1.5.3.2.3.g2f2dcc-dirty