[PATCH v3 1/2] revision: differentiate if --no-abbrev asked explicitly

["Đoàn Trần Công Danh" <congdanhqx@gmail.com>]

When we see --no-abbrev in command's arguments, we reset the 'abbrev'
field in diff-options to 0 and this value will be looked at
diff_abbrev_oid() to decide not to truncate the object name.

In a later change, we want to extend --abbrev support to diff-patch
format. When --abbrev supporting diff-patch, we need to differentiate
those below scenarios:

* None of those options --abbrev, --no-abbrev, and --full-index are
  asked. diff-patch should keep old behavior of using DEFAULT_ABBREV
  for the index length.
* --no-abbrev is asked, diff-patch should treat this option as same as
  --full-index and show full object name in index line.

While not doing anything is very effective way to show full object id,
we couldn't differentiate if --no-abbrev or not.

We can differentiate those above scenarios by either:
* Add a new field in diff-options to mark if --no-abbrev was asked.
  With this option, we have a new field for a single purpose, and one
  more thing to worry about.
* Treat --no-abbrev as same as --full-index. This option is problematic,
  since we want to allow --abbrev overwrite --no-abbrev again.
  On the other hand, we also need to keep our promises with scripter
  who uses --full-index to ask for full object names in index line,
  so, we need to respsect --full-index regardless of --abbrev.
* Set 'abbrev' field in diff-options to the length of the hash we are
  using. With this option, we can differentiate if --no-abbrev was asked
  ('abbrev' is hash's length) or none of --[no-]abbrev was asked
  ('abbrev' is '0'), script with --full-index still works and our
  headache is kept as is.

Let's ask for full object id if we see --no-abbrev.

Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
---
 revision.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/revision.c b/revision.c
index 3dcf689341..24027b1af3 100644
--- a/revision.c
+++ b/revision.c
@@ -2430,7 +2430,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	} else if (!strcmp(arg, "--always")) {
 		revs->always_show_header = 1;
 	} else if (!strcmp(arg, "--no-abbrev")) {
-		revs->abbrev = 0;
+		revs->abbrev = hexsz;
 	} else if (!strcmp(arg, "--abbrev")) {
 		revs->abbrev = DEFAULT_ABBREV;
 	} else if (skip_prefix(arg, "--abbrev=", &optarg)) {
-- 
2.28.0.215.g32ffa52ee0