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checkout: implement "@{-N}" shortcut name for N-th last branch

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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.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Junio C Hamano 2009-01-17 17:09:53 +01:00
parent 7bbd8d6c13
commit ae5a6c3684
3 changed files with 87 additions and 2 deletions
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10
builtin-checkout.c
View file

@ -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);
}

1
cache.h
View file

@ -663,6 +663,7 @@ extern int read_ref(const char *filename, unsigned char *sha1);
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[];

78
sha1_name.c
View file

@ -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"