[PATCH] Add -O<orderfile> option to diff-* brothers.

A new diffcore filter diffcore-order is introduced.  This takes
a text file each of whose line is a shell glob pattern.  Patches
that match a glob pattern on an earlier line in the file are
output before patches that match a later line, and patches that
do not match any glob pattern are output last.

A typical orderfile for git project probably should look like
this:

    README
    Makefile
    Documentation
    *.h
    *.c

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 122 insertions, 0 deletions

diff --git a/diffcore-order.c b/diffcore-order.c
new file mode 100644
index 000000000..a03862c1c
--- /dev/null
+++ b/diffcore-order.c
@@ -0,0 +1,122 @@
+/*
+ * Copyright (C) 2005 Junio C Hamano
+ */
+#include "cache.h"
+#include "diff.h"
+#include "diffcore.h"
+#include <fnmatch.h>
+
+static char **order;
+static int order_cnt;
+
+static void prepare_order(const char *orderfile)
+{
+	int fd, cnt, pass;
+	void *map;
+	char *cp, *endp;
+	struct stat st;
+
+	if (order)
+		return;
+
+	fd = open(orderfile, O_RDONLY);
+	if (fd < 0)
+		return;
+	if (fstat(fd, &st)) {
+		close(fd);
+		return;
+	}
+	map = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
+	close(fd);
+	if (-1 == (int)(long)map)
+		return;
+	endp = map + st.st_size;
+	for (pass = 0; pass < 2; pass++) {
+		cnt = 0;
+		cp = map;
+		while (cp < endp) {
+			char *ep;
+			for (ep = cp; ep < endp && *ep != '\n'; ep++)
+				;
+			/* cp to ep has one line */
+			if (*cp == '\n' || *cp == '#')
+				; /* comment */
+			else if (pass == 0)
+				cnt++;
+			else {
+				if (*ep == '\n') {
+					*ep = 0;
+					order[cnt] = cp;
+				}
+				else {
+					order[cnt] = xmalloc(ep-cp+1);
+					memcpy(order[cnt], cp, ep-cp);
+					order[cnt][ep-cp] = 0;
+				}
+				cnt++;
+			}
+			if (ep < endp)
+				ep++;
+			cp = ep;
+		}
+		if (pass == 0) {
+			order_cnt = cnt;
+			order = xmalloc(sizeof(*order) * cnt);
+		}
+	}
+}
+
+struct pair_order {
+	struct diff_filepair *pair;
+	int orig_order;
+	int order;
+};
+
+static int match_order(const char *path)
+{
+	int i;
+	char p[PATH_MAX];
+
+	for (i = 0; i < order_cnt; i++) {
+		strcpy(p, path);
+		while (p[0]) {
+			char *cp;
+			if (!fnmatch(order[i], p, 0))
+				return i;
+			cp = strrchr(p, '/');
+			if (!cp)
+				break;
+			*cp = 0;
+		}
+	}
+	return order_cnt;
+}
+
+static int compare_pair_order(const void *a_, const void *b_)
+{
+	struct pair_order const *a, *b;
+	a = (struct pair_order const *)a_;
+	b = (struct pair_order const *)b_;
+	if (a->order != b->order)
+		return a->order - b->order;
+	return a->orig_order - b->orig_order;
+}
+
+void diffcore_order(const char *orderfile)
+{
+	struct diff_queue_struct *q = &diff_queued_diff;
+	struct pair_order *o = xmalloc(sizeof(*o) * q->nr);
+	int i;
+
+	prepare_order(orderfile);
+	for (i = 0; i < q->nr; i++) {
+		o[i].pair = q->queue[i];
+		o[i].orig_order = i;
+		o[i].order = match_order(o[i].pair->two->path);
+	}
+	qsort(o, q->nr, sizeof(*o), compare_pair_order);
+	for (i = 0; i < q->nr; i++)
+		q->queue[i] = o[i].pair;
+	free(o);
+	return;
+}