Re: [PATCH v2] Add note that conflict resolution is still performed

Junio C Hamano [off-list ref] writes:

A tangent that may be worth thinking about, that does not have to be
part of this topic (as it probably will involve code change).

It makes sense that "--no-rerere-autoupdate" does not disable the
"rerere" mechanism (when it is enabled, of course), because it makes
sense to reuse recorded resolution without updating the index with
the result.

However, it may make sense to have "--rerere-autoupdate" option to
enable the "rerere" mechanism when it is disabled, because with
"rerere" disabled, there is nothing to auto-update.

I think the damage to the code to implement the above may not be too
bad.  Here is an illustration (not even compile tested) of the idea:

 - Earlier, after reading the config, we asked is_rerere_enabled()
   and let its logic decide if rerere is to be used, giving no
   influence to the incoming "flags" parameter.  Then the value of
   rerere_autoupdate read from the config is further adjusted by the
   value in "flags" parameter that relays --[no-]rerere-autoupdate
   from the command line.

 - Instead, after reading the config, we can tweak it with the
   "flags", and flip rerere_enabled to true if autoupdate is
   enabled, before making a call to is_rerere_enabled().

I do not think we have a test that insists that rerere does not kick
in in a repository where rerere is disabled and the command line
asks for "--rerere-autoupdate", so I suspect that with this patch, I
would not be surprised if no test breaks.  If we think this takes us
in a good direction, we should add a few tests to make sure at least
the following two:

 - In a repository with rerere disabled, running a command with the
   "--rerere-autoupdate" option will enable rerere for that single
   invocation of the command.

 - In a repository with rerere enabled, running a command with the
   "--no-rerere-autoupdate" option does not disable rerere for that
   single invocation of the command.

---

 rerere.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git c/rerere.c w/rerere.c
index 876ab435da..16d3e865e6 100644
--- c/rerere.c
+++ w/rerere.c

@@ -872,11 +872,13 @@ int setup_rerere(struct repository *r, struct string_list *merge_rr, int flags)
 	int fd;
 
 	git_rerere_config();
+	if (flags & (RERERE_AUTOUPDATE|RERERE_NOAUTOUPDATE))
+		rerere_autoupdate = !!(flags & RERERE_AUTOUPDATE);
+	if (rerere_autoupdate)
+		rerere_enabled = 1;
 	if (!is_rerere_enabled())
 		return -1;
 
-	if (flags & (RERERE_AUTOUPDATE|RERERE_NOAUTOUPDATE))
-		rerere_autoupdate = !!(flags & RERERE_AUTOUPDATE);
 	if (flags & RERERE_READONLY)
 		fd = 0;
 	else