[PATCH/RFC v4 1/5] checkout: implement "@{-N}" shortcut name for N-th last branch
From: Junio C Hamano <gitster@pobox.com>
Implement a shortcut @{-N} for the N-th last branch checked out, that
works by parsing the reflog for the message added by previous
git-checkout invocations. We expand the @{-N} to the branch name, so
that you end up on an attached HEAD on that branch.
---
builtin-checkout.c | 10 +++++-
cache.h | 1 +
sha1_name.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 87 insertions(+), 2 deletions(-)diff --git a/builtin-checkout.c b/builtin-checkout.c
index b5dd9c0..a3b69d6 100644
--- a/builtin-checkout.c
+++ b/builtin-checkout.c
@@ -361,8 +361,14 @@ struct branch_info {
static void setup_branch_path(struct branch_info *branch)
{
struct strbuf buf = STRBUF_INIT;
- strbuf_addstr(&buf, "refs/heads/");
- strbuf_addstr(&buf, branch->name);
+
+ if (!interpret_nth_last_branch(branch->name, &buf)) {
+ branch->name = xstrdup(buf.buf);
+ strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
+ } else {
+ strbuf_addstr(&buf, "refs/heads/");
+ strbuf_addstr(&buf, branch->name);
+ }
branch->path = strbuf_detach(&buf, NULL);
}
diff --git a/cache.h b/cache.h
index 8e1af26..0dd9168 100644
--- a/cache.h
+++ b/cache.h
@@ -663,6 +663,7 @@ static inline unsigned int hexval(unsigned char c)
extern const char *resolve_ref(const char *path, unsigned char *sha1, int, int *);
extern int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref);
extern int dwim_log(const char *str, int len, unsigned char *sha1, char **ref);
+extern int interpret_nth_last_branch(const char *str, struct strbuf *);
extern int refname_match(const char *abbrev_name, const char *full_name, const char **rules);
extern const char *ref_rev_parse_rules[];
diff --git a/sha1_name.c b/sha1_name.c
index 159c2ab..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"
--
1.6.1.315.g92577
Thomas Rast <trast@student.ethz.ch>