sha1_name: tweak @{-N} lookup

Have the lookup only look at "interesting" checkouts, meaning those
that tell you "Already on ..." don't count even though they also cause
a reflog entry.

Let interpret_nth_last_branch() return the number of characters
parsed, so that git-checkout can verify that the branch spec was
@{-N}, not @{-1}^2 or something like that.  (The latter will be added
later.)

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-checkout.c b/builtin-checkout.c
index a3b69d6b94dce47b3341f5eb77ae4438bae20cc6..dc1de06279e2fcdb945e3ec5bdcd0a6f7d06e51b 100644 (file)
--- a/builtin-checkout.c
+++ b/builtin-checkout.c
@@ -361,8 +361,10 @@ struct branch_info {
 static void setup_branch_path(struct branch_info *branch)
 {
        struct strbuf buf = STRBUF_INIT;
+       int ret;
 
-       if (!interpret_nth_last_branch(branch->name, &buf)) {
+       if ((ret = interpret_nth_last_branch(branch->name, &buf))
+           && ret == strlen(branch->name)) {
                branch->name = xstrdup(buf.buf);
                strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
        } else {

diff --git a/sha1_name.c b/sha1_name.c
index 6377264300c134db82354d11a5dd62fd7b783a59..34e39db6518f0f588e5daa7a8a0e804db570d413 100644 (file)
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -685,29 +685,28 @@ static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
                                  const char *message, void *cb_data)
 {
        struct grab_nth_branch_switch_cbdata *cb = cb_data;
-       const char *match = NULL;
-
-       if (!prefixcmp(message, "checkout: moving to "))
-               match = message + strlen("checkout: moving to ");
-       else if (!prefixcmp(message, "checkout: moving from ")) {
-               const char *cp = message + strlen("checkout: moving from ");
-               if ((cp = strstr(cp, " to ")) != NULL) {
-                       match = cp + 4;
-               }
+       const char *match = NULL, *target = NULL;
+       size_t len;
+
+       if (!prefixcmp(message, "checkout: moving from ")) {
+               match = message + strlen("checkout: moving from ");
+               if ((target = strstr(match, " to ")) != NULL)
+                       target += 4;
        }
 
        if (!match)
                return 0;
 
+       len = target - match - 4;
+       if (target[len] == '\n' && !strncmp(match, target, len))
+               return 0;
+
        if (cb->counting) {
                cb->nth++;
                return 0;
        }
 
-       if (--cb->nth <= 0) {
-               size_t len = strlen(match);
-               while (match[len-1] == '\n')
-                       len--;
+       if (cb->nth-- <= 0) {
                strbuf_reset(cb->buf);
                strbuf_add(cb->buf, match, len);
                return 1;
@@ -718,26 +717,28 @@ static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 /*
  * This reads "@{-N}" syntax, finds the name of the Nth previous
  * branch we were on, and places the name of the branch in the given
- * buf and returns 0 if successful.
+ * buf and returns the number of characters parsed if successful.
  *
  * If the input is not of the accepted format, it returns a negative
  * number to signal an error.
+ *
+ * If the input was ok but there are not N branch switches in the
+ * reflog, it returns 0.
  */
 int interpret_nth_last_branch(const char *name, struct strbuf *buf)
 {
-       int nth, i;
+       int nth;
        struct grab_nth_branch_switch_cbdata cb;
+       const char *brace;
+       char *num_end;
 
        if (name[0] != '@' || name[1] != '{' || name[2] != '-')
                return -1;
-       for (i = 3, nth = 0; name[i] && name[i] != '}'; i++) {
-               char ch = name[i];
-               if ('0' <= ch && ch <= '9')
-                       nth = nth * 10 + ch - '0';
-               else
-                       return -1;
-       }
-       if (nth < 0 || 10 <= nth)
+       brace = strchr(name, '}');
+       if (!brace)
+               return -1;
+       nth = strtol(name+3, &num_end, 10);
+       if (num_end != brace)
                return -1;
 
        cb.counting = 1;
@@ -745,11 +746,15 @@ int interpret_nth_last_branch(const char *name, struct strbuf *buf)
        cb.buf = buf;
        for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
 
+       if (cb.nth < nth)
+               return 0;
+
        cb.counting = 0;
        cb.nth -= nth;
        cb.buf = buf;
        for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
-       return 0;
+
+       return brace-name+1;
 }
 
 /*