Re: [PATCH v3 1/5] stat_tracking_info: return +1 when branches not equal

[Junio C Hamano]

Jeff Hostetler  writes:

> - if (stat_tracking_info(branch, _ours,
> -_theirs, NULL)) {
> + if (stat_tracking_info(branch, _ours, _theirs,
> +NULL, AHEAD_BEHIND_FULL) < 0) {
> ...
> - if (stat_tracking_info(branch, _ours,
> -_theirs, NULL))
> + if (stat_tracking_info(branch, _ours, _theirs,
> +NULL, AHEAD_BEHIND_FULL) < 0)

Mental note: any code that reacted to stat_tracking_info() returning
non-zero was reacting to "no useful info in num_{ours,theirs}".
They now have to compare the returned value with "< 0" for the same
purpose.

> ...
>   * Returns -1 if num_ours and num_theirs could not be filled in (e.g., no
> - * upstream defined, or ref does not exist), 0 otherwise.
> + * upstream defined, or ref does not exist).  Returns 0 if the commits are
> + * identical.  Returns 1 if commits are different.
>   */
>  int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
> -const char **upstream_name)
> +const char **upstream_name, enum ahead_behind_flags abf)
>  {
>   struct object_id oid;
>   struct commit *ours, *theirs;
> @@ -2019,6 +2026,8 @@ int stat_tracking_info(struct branch *branch, int 
> *num_ours, int *num_theirs,
>   *num_theirs = *num_ours = 0;
>   return 0;
>   }
> + if (abf == AHEAD_BEHIND_QUICK)
> + return 1;
> ...
>   argv_array_clear();
> - return 0;
> + return 1;
>  }

When a caller gets +1 from the function, it is not safe to peek into
*num_{ours,theirs} if it passed _QUICK.

> @@ -2064,7 +2073,8 @@ int format_tracking_info(struct branch *branch, struct 
> strbuf *sb)
> - if (stat_tracking_info(branch, , , _base) < 0) {
> + if (stat_tracking_info(branch, , , _base,
> +AHEAD_BEHIND_FULL) < 0) {

Sane conversion to the new return value convention.

> diff --git a/wt-status.c b/wt-status.c
> index 94e5eba..8f7fdc6 100644
> --- a/wt-status.c
> +++ b/wt-status.c
> @@ -1791,7 +1791,8 @@ static void wt_shortstatus_print_tracking(struct 
> wt_status *s)
>  
>   color_fprintf(s->fp, branch_color_local, "%s", branch_name);
>  
> - if (stat_tracking_info(branch, _ours, _theirs, ) < 0) {
> + if (stat_tracking_info(branch, _ours, _theirs, ,
> +AHEAD_BEHIND_FULL) < 0) {

Ditto.

> @@ -1928,7 +1929,8 @@ static void wt_porcelain_v2_print_tracking(struct 
> wt_status *s)
>   /* Lookup stats on the upstream tracking branch, if set. */
>   branch = branch_get(branch_name);
>   base = NULL;
> - ab_info = (stat_tracking_info(branch, _ahead, _behind, 
> ) == 0);
> + ab_info = (stat_tracking_info(branch, _ahead, _behind,
> +   , AHEAD_BEHIND_FULL) >= 0);

If a later step plans to (conditionally) allow _QUICK to be passed
here, this conversion is questionable, because ab_info being true
no longer is a sign that nr_{ahead,behind} are valid.

I suspect that moving the "s/ab_info/sti/" bits around here from
step [2/5] to this commit may make the result after this patch more
consistent, but it is not a big deal either way.

>   if (base) {
>   base = shorten_unambiguous_ref(base, 0);
>   fprintf(s->fp, "# branch.upstream %s%c", base, eol);

[PATCH v3 1/5] stat_tracking_info: return +1 when branches not equal

[Jeff Hostetler]

From: Jeff Hostetler 

Extend stat_tracking_info() to return +1 when branches are not equal and to
take a new "enum ahead_behind_flags" argument to allow skipping the (possibly
expensive) ahead/behind computation.

This will be used in the next commit to allow "git status" to avoid full
ahead/behind calculations for performance reasons.

Signed-off-by: Jeff Hostetler 
---
 ref-filter.c |  8 
 remote.c | 26 ++
 remote.h |  8 +++-
 wt-status.c  |  6 --
 4 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/ref-filter.c b/ref-filter.c
index e728b15..23bcdc4 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -1238,8 +1238,8 @@ static void fill_remote_ref_details(struct used_atom 
*atom, const char *refname,
if (atom->u.remote_ref.option == RR_REF)
*s = show_ref(>u.remote_ref.refname, refname);
else if (atom->u.remote_ref.option == RR_TRACK) {
-   if (stat_tracking_info(branch, _ours,
-  _theirs, NULL)) {
+   if (stat_tracking_info(branch, _ours, _theirs,
+  NULL, AHEAD_BEHIND_FULL) < 0) {
*s = xstrdup(msgs.gone);
} else if (!num_ours && !num_theirs)
*s = "";
@@ -1256,8 +1256,8 @@ static void fill_remote_ref_details(struct used_atom 
*atom, const char *refname,
free((void *)to_free);
}
} else if (atom->u.remote_ref.option == RR_TRACKSHORT) {
-   if (stat_tracking_info(branch, _ours,
-  _theirs, NULL))
+   if (stat_tracking_info(branch, _ours, _theirs,
+  NULL, AHEAD_BEHIND_FULL) < 0)
return;
 
if (!num_ours && !num_theirs)
diff --git a/remote.c b/remote.c
index b220f0d..ca5a416 100644
--- a/remote.c
+++ b/remote.c
@@ -1977,16 +1977,23 @@ int ref_newer(const struct object_id *new_oid, const 
struct object_id *old_oid)
 }
 
 /*
- * Compare a branch with its upstream, and save their differences (number
- * of commits) in *num_ours and *num_theirs. The name of the upstream branch
- * (or NULL if no upstream is defined) is returned via *upstream_name, if it
- * is not itself NULL.
+ * Lookup the upstream branch for the given branch and if present, optionally
+ * compute the commit ahead/behind values for the pair.
+ *
+ * If abf is AHEAD_BEHIND_FULL, compute the full ahead/behind and return the
+ * counts in *num_ours and *num_theirs.  If abf is AHEAD_BEHIND_QUICK, skip
+ * the (potentially expensive) a/b computation (*num_ours and *num_theirs are
+ * left undefined).
+ *
+ * The name of the upstream branch (or NULL if no upstream is defined) is
+ * returned via *upstream_name, if it is not itself NULL.
  *
  * Returns -1 if num_ours and num_theirs could not be filled in (e.g., no
- * upstream defined, or ref does not exist), 0 otherwise.
+ * upstream defined, or ref does not exist).  Returns 0 if the commits are
+ * identical.  Returns 1 if commits are different.
  */
 int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
-  const char **upstream_name)
+  const char **upstream_name, enum ahead_behind_flags abf)
 {
struct object_id oid;
struct commit *ours, *theirs;
@@ -2019,6 +2026,8 @@ int stat_tracking_info(struct branch *branch, int 
*num_ours, int *num_theirs,
*num_theirs = *num_ours = 0;
return 0;
}
+   if (abf == AHEAD_BEHIND_QUICK)
+   return 1;
 
/* Run "rev-list --left-right ours...theirs" internally... */
argv_array_push(, ""); /* ignored */
@@ -2051,7 +2060,7 @@ int stat_tracking_info(struct branch *branch, int 
*num_ours, int *num_theirs,
clear_commit_marks(theirs, ALL_REV_FLAGS);
 
argv_array_clear();
-   return 0;
+   return 1;
 }
 
 /*
@@ -2064,7 +2073,8 @@ int format_tracking_info(struct branch *branch, struct 
strbuf *sb)
char *base;
int upstream_is_gone = 0;
 
-   if (stat_tracking_info(branch, , , _base) < 0) {
+   if (stat_tracking_info(branch, , , _base,
+  AHEAD_BEHIND_FULL) < 0) {
if (!full_base)
return 0;
upstream_is_gone = 1;
diff --git a/remote.h b/remote.h
index 2ecf4c8..00932f5 100644
--- a/remote.h
+++ b/remote.h
@@ -255,9 +255,15 @@ enum match_refs_flags {
MATCH_REFS_FOLLOW_TAGS  = (1 << 3)
 };
 
+/* Flags for --ahead-behind option. */
+enum ahead_behind_flags {
+   AHEAD_BEHIND_QUICK = 0,  /* just eq/neq reporting */
+   AHEAD_BEHIND_FULL  = 1,  /* traditional a/b reporting */
+};
+
 /* Reporting of tracking info */
 int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
-