sha1_name: add get_sha1_with_context()

Textconv is defined by the diff driver, which is associated with a pathname,
not a blob. This fonction permits to know the context for the sha1 you're
looking for, especially his pathname

Signed-off-by: Clément Poulain <clement.poulain@ensimag.imag.fr>
Signed-off-by: Diane Gasselin <diane.gasselin@ensimag.imag.fr>
Signed-off-by: Axel Bonnet <axel.bonnet@ensimag.imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -730,12 +730,23 @@ static inline unsigned int hexval(unsigned char c)
 #define MINIMUM_ABBREV 4
 #define DEFAULT_ABBREV 7
 
+struct object_context {
+	unsigned char tree[20];
+	char path[PATH_MAX];
+	unsigned mode;
+};
+
 extern int get_sha1(const char *str, unsigned char *sha1);
 extern int get_sha1_with_mode_1(const char *str, unsigned char *sha1, unsigned *mode, int gently, const char *prefix);
 static inline int get_sha1_with_mode(const char *str, unsigned char *sha1, unsigned *mode)
 {
 	return get_sha1_with_mode_1(str, sha1, mode, 1, NULL);
 }
+extern int get_sha1_with_context_1(const char *name, unsigned char *sha1, struct object_context *orc, int gently, const char *prefix);
+static inline int get_sha1_with_context(const char *str, unsigned char *sha1, struct object_context *orc)
+{
+	return get_sha1_with_context_1(str, sha1, orc, 1, NULL);
+}
 extern int get_sha1_hex(const char *hex, unsigned char *sha1);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern int read_ref(const char *filename, unsigned char *sha1);

sha1_name.c

@@ -933,8 +933,8 @@ int interpret_branch_name(const char *name, struct strbuf *buf)
  */
 int get_sha1(const char *name, unsigned char *sha1)
 {
-	unsigned unused;
-	return get_sha1_with_mode(name, sha1, &unused);
+	struct object_context unused;
+	return get_sha1_with_context(name, sha1, &unused);
 }
 
 /* Must be called only when object_name:filename doesn't exist. */
@@ -1031,12 +1031,24 @@ static void diagnose_invalid_index_path(int stage,
 
 
 int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode, int gently, const char *prefix)
+{
+	struct object_context oc;
+	int ret;
+	ret = get_sha1_with_context_1(name, sha1, &oc, gently, prefix);
+	*mode = oc.mode;
+	return ret;
+}
+
+int get_sha1_with_context_1(const char *name, unsigned char *sha1,
+			    struct object_context *oc,
+			    int gently, const char *prefix)
 {
 	int ret, bracket_depth;
 	int namelen = strlen(name);
 	const char *cp;
 
-	*mode = S_IFINVALID;
+	memset(oc, 0, sizeof(*oc));
+	oc->mode = S_IFINVALID;
 	ret = get_sha1_1(name, namelen, sha1);
 	if (!ret)
 		return ret;
@@ -1059,6 +1071,11 @@ int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode,
 			cp = name + 3;
 		}
 		namelen = namelen - (cp - name);
+
+		strncpy(oc->path, cp,
+			sizeof(oc->path));
+		oc->path[sizeof(oc->path)-1] = '\0';
+
 		if (!active_cache)
 			read_cache();
 		pos = cache_name_pos(cp, namelen);
@@ -1071,7 +1088,6 @@ int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode,
 				break;
 			if (ce_stage(ce) == stage) {
 				hashcpy(sha1, ce->sha1);
-				*mode = ce->ce_mode;
 				return 0;
 			}
 			pos++;
@@ -1098,12 +1114,17 @@ int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode,
 		}
 		if (!get_sha1_1(name, cp-name, tree_sha1)) {
 			const char *filename = cp+1;
-			ret = get_tree_entry(tree_sha1, filename, sha1, mode);
+			ret = get_tree_entry(tree_sha1, filename, sha1, &oc->mode);
 			if (!gently) {
 				diagnose_invalid_sha1_path(prefix, filename,
 							   tree_sha1, object_name);
 				free(object_name);
 			}
+			hashcpy(oc->tree, tree_sha1);
+			strncpy(oc->path, filename,
+				sizeof(oc->path));
+			oc->path[sizeof(oc->path)-1] = '\0';
+
 			return ret;
 		} else {
 			if (!gently)