[PATCH] diff --stat: do not drop rename information.

[PATCH] diff --stat: do not drop rename information.

[Junio C Hamano]

When a verbatim rename or copy is detected, we did not show
anything on the "diff --stat" for the filepair.  This makes it
to show the rename information.

Signed-off-by: Junio C Hamano <junkio@cox.net>

---
 * In git.git itself, with and without this patch:

        $ git-diff-tree --stat -M ba580ae
        ba580aeafb52921025de1efe1c50db34393f9907
         Makefile |    2 +-
         1 files changed, 1 insertions(+), 1 deletions(-)

        $ git-diff-tree --stat -M ba580ae
        ba580aeafb52921025de1efe1c50db34393f9907
         Makefile             |    2 +-
         diff.c => diff-lib.c |    0
         2 files changed, 1 insertions(+), 1 deletions(-)

   Since renames are rare, I think this is a good change.  We
   might want to do the same for "apply --stat" as well.

 diff-lib.c |   98 ++++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 files changed, 81 insertions(+), 17 deletions(-)

9ea8da8f01d7fb2159a81edba9e5e7885e6b616e
diff --git a/diff-lib.c b/diff-lib.c
index 0a832c3..86d1417 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -201,7 +201,8 @@ struct diffstat_t {
 	int nr;
 	int alloc;
 	struct diffstat_file {
-		char *name;
+		char *name_a;
+		char *name_b;
 		unsigned is_unmerged:1;
 		unsigned is_binary:1;
 		unsigned int added, deleted;
@@ -209,7 +210,8 @@ struct diffstat_t {
 };
 
 static struct diffstat_file *diffstat_add(struct diffstat_t *diffstat,
-		const char *name)
+					  char *name_a,
+					  char *name_b)
 {
 	struct diffstat_file *x;
 	x = xcalloc(sizeof (*x), 1);
@@ -219,7 +221,10 @@ static struct diffstat_file *diffstat_ad
 				diffstat->alloc * sizeof(x));
 	}
 	diffstat->files[diffstat->nr++] = x;
-	x->name = strdup(name);
+	x->name_a = strdup(name_a);
+	if (name_b)
+		name_b = strdup(name_b);
+	x->name_b = name_b;
 	return x;
 }
 
@@ -234,6 +239,54 @@ static void diffstat_consume(void *priv,
 		x->deleted++;
 }
 
+static char *find_common_pfx(const char *a, const char *b)
+{
+	const char *old = a;
+	const char *new = b;
+	char *name = NULL;
+	int common_length;
+	int len_a = strlen(a);
+	int len_b = strlen(b);
+
+	/* Find common prefix */
+	while (1) {
+		const char *slash_old, *slash_new;
+		slash_old = strchr(old, '/');
+		slash_new = strchr(new, '/');
+		if (!slash_old ||
+		    !slash_new ||
+		    slash_old - old != slash_new - new ||
+		    memcmp(old, new, slash_new - new))
+			break;
+		old = slash_old + 1;
+		new = slash_new + 1;
+	}
+	/* a thru old is the common prefix, and old and new
+	 * through the end of names are renames.
+	 * Either give
+	 * 	common{suffix-a => suffix-b}
+	 * or
+	 *      name-a => name-b
+	 * whichever is shorter.
+	 */
+	common_length = (old - a);
+	/*
+	  int squashed_len = (len_a + len_b - common_length + 6);
+	  int separate_len = (len_a + len_b) + 4;
+	*/
+	if (common_length < 2) {
+		/* no point squashing */
+		name = xmalloc(len_a + len_b + 5);
+		sprintf(name, "%s => %s", a, b);
+	}
+	else {
+		name = xmalloc(len_a + len_b - common_length + 7);
+		sprintf(name, "%.*s{%s => %s}",
+			common_length, a, old, new);
+	}
+	return name;
+}
+
 static const char pluses[] = "++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++";
 static const char minuses[]= "----------------------------------------------------------------------";
 
@@ -249,8 +302,15 @@ static void show_stats(struct diffstat_t
 
 	for (i = 0; i < data->nr; i++) {
 		struct diffstat_file *file = data->files[i];
-
-		len = strlen(file->name);
+		char *name = file->name_a;
+		if (file->name_b && strcmp(name, file->name_b)) {
+			name = find_common_pfx(name, file->name_b);
+			if (name != file->name_a) {
+				free(file->name_a);
+				file->name_a = name;
+			}
+		}
+		len = strlen(name);
 		if (max_len < len)
 			max_len = len;
 
@@ -261,7 +321,7 @@ static void show_stats(struct diffstat_t
 	}
 
 	for (i = 0; i < data->nr; i++) {
-		char *name = data->files[i]->name;
+		char *name = data->files[i]->name_a;
 		int added = data->files[i]->added;
 		int deleted = data->files[i]->deleted;
 
@@ -269,7 +329,7 @@ static void show_stats(struct diffstat_t
 			char *qname = xmalloc(len + 1);
 			quote_c_style(name, qname, NULL, 0);
 			free(name);
-			data->files[i]->name = name = qname;
+			data->files[i]->name_a = name = qname;
 		}
 
 		/*
@@ -305,6 +365,8 @@ static void show_stats(struct diffstat_t
 			printf(" %s%-*s |  Unmerged\n", prefix, len, name);
 			goto free_diffstat_file;
 		}
+		else if (data->files[i]->name_b)
+			;
 		else if (added + deleted == 0) {
 			total_files--;
 			goto free_diffstat_file;
@@ -325,7 +387,8 @@ static void show_stats(struct diffstat_t
 				len, name, added + deleted,
 				add, pluses, del, minuses);
 	free_diffstat_file:
-		free(data->files[i]->name);
+		free(data->files[i]->name_a);
+		free(data->files[i]->name_b);
 		free(data->files[i]);
 	}
 	free(data->files);
@@ -424,14 +487,15 @@ static void builtin_diff(const char *nam
 	return;
 }
 
-static void builtin_diffstat(const char *name_a, const char *name_b,
-		struct diff_filespec *one, struct diff_filespec *two,
-		struct diffstat_t *diffstat)
+static void builtin_diffstat(char *name_a, char *name_b,
+			     struct diff_filespec *one,
+			     struct diff_filespec *two,
+			     struct diffstat_t *diffstat)
 {
 	mmfile_t mf1, mf2;
 	struct diffstat_file *data;
 
-	data = diffstat_add(diffstat, name_a ? name_a : name_b);
+	data = diffstat_add(diffstat, name_a, name_b);
 
 	if (!one || !two) {
 		data->is_unmerged = 1;
@@ -992,10 +1056,10 @@ static void run_diff(struct diff_filepai
 }
 
 static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
-		struct diffstat_t *diffstat)
+			 struct diffstat_t *diffstat)
 {
-	const char *name;
-	const char *other;
+	char *name;
+	char *other;
 
 	if (DIFF_PAIR_UNMERGED(p)) {
 		/* unmerged */
@@ -1374,7 +1438,7 @@ static void diff_flush_patch(struct diff
 }
 
 static void diff_flush_stat(struct diff_filepair *p, struct diff_options *o,
-		struct diffstat_t *diffstat)
+			    struct diffstat_t *diffstat)
 {
 	if (diff_unmodified_pair(p))
 		return;
@@ -1559,7 +1623,7 @@ void diff_flush(struct diff_options *opt
 		for (i = 0; i < q->nr; i++) {
 			struct diff_filepair *p = q->queue[i];
 			flush_one_pair(p, DIFF_FORMAT_DIFFSTAT, options,
-					diffstat);
+				       diffstat);
 		}
 		show_stats(diffstat);
 		free(diffstat);
-- 
1.3.0.g6057

Re: [PATCH] diff --stat: do not drop rename information.

[Johannes Schindelin]

Hi,

On Wed, 19 Apr 2006, Junio C Hamano wrote:

> When a verbatim rename or copy is detected, we did not show
> anything on the "diff --stat" for the filepair.  This makes it
> to show the rename information.

Makes sense. This also shows deletes and adds as "bla/bla => /dev/null" 
and "/dev/null => bla/bla", right?

Ciao,
Dscho

Re: [PATCH] diff --stat: do not drop rename information.

[Junio C Hamano]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> ... This also shows deletes and adds as "bla/bla => /dev/null" 
> and "/dev/null => bla/bla", right?

Dunno.  It's still essentially your code ;-).

The usual "diffstat" does not do that, but it might be useful.
Another thing that could be done is to fold in mode change
information (usually people care only about chmod +/-x).