Junio C Hamano <gits...@pobox.com> writes:

> Also, a few points this patch highlights in the code before the
> change:
>  - If we were on a branch with 40-hex name at nth prior checkout,
>    would we mistake it as being detached at the commit?
>  - If we were on a branch 'foo' at nth prior checkout, would our
>    previous get_sha1_1() have made us mistake it as referring to a
>    tag 'foo' with the same name if it exists?
> The former needs a fix to either writing of reflog or reading by
> interpret_nth_prior_checkout() so that we can tell these cases apart
> more reliably.  Then the latter can be solved by splicing
> refs/heads/ in front of the branch name before recursively calling
> get_sha1_1() in the original code (and similar fix can be
> forward-ported to this patch).
> Incidentally, I think if we prefix refs/heads/ in front and feed
> that to dwim_ref/log, we would also avoid running @{-N} twice (which
> I suspect might be more expensive than a simple recursion, as it
> needs to go through the reflog file), which may be a nice side
> effect of such a fix we would get for free.

Here is the first step (i.e. more reliable interpret_nth_prior).

I looked at all the existing callers of interpret_branch_name() and
it appears to me that most of them currently assume they are getting
a branch name, because they want to work on a ref, and some of them
do not care, because they are working on a revision.  For the
former, they can (and should) error out instead of relying on not
having refs/heads/$detached_SHA1 that will prevent them from working
on a ref which is what they currently do, if they had the "detached"
information.  For the latter, if we give "detached" information,
they can either prefix "refs/heads/" (if the result is "not
detached") to call resolve_ref(), or call get_sha1_hex (if the
result is "detached"), which would be the solution for the second
issue I noticed in the message I am replying to.

The next step on top of this patch may be to expose the "detached"
bit up in the API chain to let callers of interpret_branch_name() to
know about the distinction.

 sha1_name.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 3820f28..3dd6667 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -862,6 +862,7 @@ static int get_sha1_oneline(const char *prefix, unsigned 
char *sha1,
 struct grab_nth_branch_switch_cbdata {
        int remaining;
        struct strbuf buf;
+       int detached;
 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
@@ -880,9 +881,14 @@ static int grab_nth_branch_switch(unsigned char *osha1, 
unsigned char *nsha1,
        if (!match || !target)
                return 0;
        if (--(cb->remaining) == 0) {
+               unsigned char sha1[20];
                len = target - match;
                strbuf_add(&cb->buf, match, len);
+               cb->detached = (len == 40 &&
+                               !get_sha1_hex(match, sha1) &&
+                               !hashcmp(osha1, sha1));
                return 1; /* we are done */
        return 0;
@@ -892,7 +898,7 @@ static int grab_nth_branch_switch(unsigned char *osha1, 
unsigned char *nsha1,
  * Parse @{-N} syntax, return the number of characters parsed
  * if successful; otherwise signal an error with negative value.
-static int interpret_nth_prior_checkout(const char *name, struct strbuf *buf)
+static int interpret_nth_prior_checkout(const char *name, struct strbuf *buf, 
int *detached)
        long nth;
        int retval;
@@ -917,6 +923,8 @@ static int interpret_nth_prior_checkout(const char *name, 
struct strbuf *buf)
        if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, 
&cb)) {
                strbuf_add(buf, cb.buf.buf, cb.buf.len);
+               if (detached)
+                       *detached = cb.detached;
                retval = brace - name + 1;
@@ -992,7 +1000,7 @@ int interpret_branch_name(const char *name, struct strbuf 
        char *cp;
        struct branch *upstream;
        int namelen = strlen(name);
-       int len = interpret_nth_prior_checkout(name, buf);
+       int len = interpret_nth_prior_checkout(name, buf, NULL);
        int tmp_len;
        if (!len)
To unsubscribe from this list: send the line "unsubscribe git" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Reply via email to