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-rw-r--r--sha1_name.c78
1 files changed, 78 insertions, 0 deletions
diff --git a/sha1_name.c b/sha1_name.c
index 159c2ab8..6377264 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -674,6 +674,84 @@ static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
return retval;
}
+struct grab_nth_branch_switch_cbdata {
+ int counting;
+ int nth;
+ struct strbuf *buf;
+};
+
+static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
+ const char *email, unsigned long timestamp, int tz,
+ 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;
+ }
+ }
+
+ if (!match)
+ return 0;
+
+ if (cb->counting) {
+ cb->nth++;
+ return 0;
+ }
+
+ if (--cb->nth <= 0) {
+ size_t len = strlen(match);
+ while (match[len-1] == '\n')
+ len--;
+ strbuf_reset(cb->buf);
+ strbuf_add(cb->buf, match, len);
+ return 1;
+ }
+ return 0;
+}
+
+/*
+ * 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.
+ *
+ * If the input is not of the accepted format, it returns a negative
+ * number to signal an error.
+ */
+int interpret_nth_last_branch(const char *name, struct strbuf *buf)
+{
+ int nth, i;
+ struct grab_nth_branch_switch_cbdata cb;
+
+ 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)
+ return -1;
+
+ cb.counting = 1;
+ cb.nth = 0;
+ cb.buf = buf;
+ for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
+
+ cb.counting = 0;
+ cb.nth -= nth;
+ cb.buf = buf;
+ for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
+ return 0;
+}
+
/*
* This is like "get_sha1_basic()", except it allows "sha1 expressions",
* notably "xyz^" for "parent of xyz"