[PATCH 17/32] tree-diff: add narrow versions of diff_{root_,}tree_sha1

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

These versions assume that the given trees for diff are toplevel
trees. They simply go down to find $GIT_DIR/narrow subtree and do diff
on those trees instead. diff_tree_sha1 callers must be adapted to use
this version to support narrow repos.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 diff.h      |    5 ++++
 tree-diff.c |   74 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+), 0 deletions(-)

diff --git a/diff.h b/diff.h
index d43da9d..13b4f10 100644
--- a/diff.h
+++ b/diff.h
@@ -171,6 +171,11 @@ extern int diff_tree_sha1(const unsigned char *old, const unsigned char *new,
 extern int diff_root_tree_sha1(const unsigned char *new, const char *base,
                                struct diff_options *opt);
 
+extern int narrow_diff_tree_sha1(const unsigned char *old, const unsigned char *new,
+				 const char *base, struct diff_options *opt);
+extern int narrow_diff_root_tree_sha1(const unsigned char *new, const char *base,
+				      struct diff_options *opt);
+
 struct combine_diff_path {
 	struct combine_diff_path *next;
 	int len;
diff --git a/tree-diff.c b/tree-diff.c
index cd659c6..31b0842 100644
--- a/tree-diff.c
+++ b/tree-diff.c
@@ -433,6 +433,45 @@ int diff_tree_sha1(const unsigned char *old, const unsigned char *new, const cha
 	return retval;
 }
 
+int narrow_diff_tree_sha1(const unsigned char *old, const unsigned char *new, const char *base, struct diff_options *opt)
+{
+	unsigned char old2[20], new2[20];
+	char *new_base = NULL;
+	int retval;
+
+	if (get_narrow_prefix()) {
+		int len1 = strlen(get_narrow_prefix());
+		int len2 = base ? strlen(base) : 0;
+		unsigned long size;
+		unsigned char deref_sha1[20];
+
+		if (len2 && !strncmp(base, get_narrow_prefix(), len1) &&
+		    (base[len1] == '/' || base[len1] == '\0'))
+			;	/* good */
+		else {
+			new_base = xmalloc(len1 + 1 + len2 + 1);
+			memcpy(new_base, get_narrow_prefix, len1+1);
+			if (len2) {
+				new_base[len1] = '/';
+				memcpy(new_base+len1+1, base, len2+1);
+			}
+			base = new_base;
+		}
+
+		free(read_object_with_reference(old, tree_type, &size, deref_sha1));
+		if (!find_tree(deref_sha1, old2, get_narrow_prefix()))
+			hashcpy(old2, (const unsigned char *)EMPTY_TREE_SHA1_BIN);
+		old = old2;
+		free(read_object_with_reference(new, tree_type, &size, deref_sha1));
+		if (!find_tree(deref_sha1, new2, get_narrow_prefix()))
+			hashcpy(new2, (const unsigned char *)EMPTY_TREE_SHA1_BIN);
+		new = new2;
+	}
+	retval = diff_tree_sha1(old, new, base, opt);
+	free(new_base);
+	return retval;
+}
+
 int diff_root_tree_sha1(const unsigned char *new, const char *base, struct diff_options *opt)
 {
 	int retval;
@@ -451,6 +490,41 @@ int diff_root_tree_sha1(const unsigned char *new, const char *base, struct diff_
 	return retval;
 }
 
+int narrow_diff_root_tree_sha1(const unsigned char *new, const char *base, struct diff_options *opt)
+{
+	unsigned char new2[20];
+	char *new_base = NULL;
+	int retval;
+
+	if (get_narrow_prefix()) {
+		int len1 = strlen(get_narrow_prefix());
+		int len2 = base ? strlen(base) : 0;
+		unsigned long size;
+		unsigned char deref_sha1[20];
+
+		if (len2 && !strncmp(base, get_narrow_prefix(), len1) &&
+		    (base[len1] == '/' || base[len1] == '\0'))
+			;	/* good */
+		else {
+			new_base = xmalloc(len1 + 1 + len2 + 1);
+			memcpy(new_base, get_narrow_prefix, len1+1);
+			if (len2) {
+				new_base[len1] = '/';
+				memcpy(new_base+len1+1, base, len2+1);
+			}
+			base = new_base;
+		}
+
+		free(read_object_with_reference(new, tree_type, &size, deref_sha1));
+		if (!find_tree(deref_sha1, new2, get_narrow_prefix()))
+			hashcpy(new2, (const unsigned char *)EMPTY_TREE_SHA1_BIN);
+		new = new2;
+	}
+	retval = diff_root_tree_sha1(new, base, opt);
+	free(new_base);
+	return retval;
+}
+
 static int count_paths(const char **paths)
 {
 	int i = 0;
-- 
1.7.1.rc1.69.g24c2f7