1 files changed, 84 insertions, 0 deletions
diff --git a/archive.c b/archive.c
new file mode 100644
index 0000000000..fb159fe59e
--- /dev/null
+++ b/archive.c
@@ -0,0 +1,84 @@
+#include "cache.h"
+#include "commit.h"
+#include "attr.h"
+
+static void format_subst(const struct commit *commit,
+                         const char *src, size_t len,
+                         struct strbuf *buf)
+{
+	char *to_free = NULL;
+	struct strbuf fmt;
+
+	if (src == buf->buf)
+		to_free = strbuf_detach(buf, NULL);
+	strbuf_init(&fmt, 0);
+	for (;;) {
+		const char *b, *c;
+
+		b = memmem(src, len, "$Format:", 8);
+		if (!b || src + len < b + 9)
+			break;
+		c = memchr(b + 8, '$', len - 8);
+		if (!c)
+			break;
+
+		strbuf_reset(&fmt);
+		strbuf_add(&fmt, b + 8, c - b - 8);
+
+		strbuf_add(buf, src, b - src);
+		format_commit_message(commit, fmt.buf, buf);
+		len -= c + 1 - src;
+		src  = c + 1;
+	}
+	strbuf_add(buf, src, len);
+	strbuf_release(&fmt);
+	free(to_free);
+}
+
+static int convert_to_archive(const char *path,
+                              const void *src, size_t len,
+                              struct strbuf *buf,
+                              const struct commit *commit)
+{
+	static struct git_attr *attr_export_subst;
+	struct git_attr_check check[1];
+
+	if (!commit)
+		return 0;
+
+	if (!attr_export_subst)
+		attr_export_subst = git_attr("export-subst", 12);
+
+	check[0].attr = attr_export_subst;
+	if (git_checkattr(path, ARRAY_SIZE(check), check))
+		return 0;
+	if (!ATTR_TRUE(check[0].value))
+		return 0;
+
+	format_subst(commit, src, len, buf);
+	return 1;
+}
+
+void *sha1_file_to_archive(const char *path, const unsigned char *sha1,
+                           unsigned int mode, enum object_type *type,
+                           unsigned long *sizep,
+                           const struct commit *commit)
+{
+	void *buffer;
+
+	buffer = read_sha1_file(sha1, type, sizep);
+	if (buffer && S_ISREG(mode)) {
+		struct strbuf buf;
+		size_t size = 0;
+
+		strbuf_init(&buf, 0);
+		strbuf_attach(&buf, buffer, *sizep, *sizep + 1);
+		convert_to_working_tree(path, buf.buf, buf.len, &buf);
+		convert_to_archive(path, buf.buf, buf.len, &buf, commit);
+		buffer = strbuf_detach(&buf, &size);
+		*sizep = size;
+	}
+
+	return buffer;
+}
+