[PATCH] Introduce diff-tree-helper.

This patch introduces a new program, diff-tree-helper.  It reads
output from diff-cache and diff-tree, and produces a patch file.
The diff format customization can be done the same way the
show-diff uses; the same external diff interface introduced by
the previous patch to drive diff from show-diff is used so this
is not surprising.

It is used like the following examples:

   $ diff-cache --cached -z <tree> | diff-tree-helper -z -R paths...
   $ diff-tree -r -z <tree1> <tree2> | diff-tree-helper -z paths...

 - As usual, the use of the -z flag is recommended in the script
   to pass NUL-terminated filenames through the pipe between
   commands.

 - The -R flag is used to generate reverse diff.  It does not
   matter for diff-tree case, but it is sometimes useful to get
   a patch in the desired direction out of diff-cache.

 - The paths parameters are used to restrict the paths that
   appears in the output.  Again this is useful to use with
   diff-cache, which, unlike diff-tree, does not take such paths
   restriction parameters.

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

1 files changed, 43 insertions, 0 deletions

diff --git a/strbuf.c b/strbuf.c
new file mode 100644
index 0000000000..dac945c7c8
--- /dev/null
+++ b/strbuf.c
@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "strbuf.h"
+
+void strbuf_init(struct strbuf *sb) {
+	sb->buf = 0;
+	sb->eof = sb->alloc = sb->len = 0;
+}
+
+static void strbuf_begin(struct strbuf *sb) {
+	free(sb->buf);
+	strbuf_init(sb);
+}
+
+static void inline strbuf_add(struct strbuf *sb, int ch) {
+	if (sb->alloc <= sb->len) {
+		sb->alloc = sb->alloc * 3 / 2 + 16;
+		sb->buf = realloc(sb->buf, sb->alloc);
+	}
+	sb->buf[sb->len++] = ch;
+}
+
+static void strbuf_end(struct strbuf *sb) {
+	strbuf_add(sb, 0);
+}
+
+void read_line(struct strbuf *sb, FILE *fp, int term) {
+	int ch;
+	strbuf_begin(sb);
+	if (feof(fp)) {
+		sb->eof = 1;
+		return;
+	}
+	while ((ch = fgetc(fp)) != EOF) {
+		if (ch == term)
+			break;
+		strbuf_add(sb, ch);
+	}
+	if (sb->len == 0)
+		sb->eof = 1;
+	strbuf_end(sb);
+}
+