Re: [PATCH 3/6] fsmonitor: Update helper tool, now that flags are filled later

[Alex Vandiver <alexmv@dropbox.com>]

On Mon, 18 Dec 2017, Alex Vandiver wrote:
> dd9005a0a ("fsmonitor: delay updating state until after split index is
> merged", 2017-10-27) began deferring the setting of the
> CE_FSMONITOR_VALID flag until later, such that do_read_index() does
> not perform those steps.  This means that t/helper/test-dump-fsmonitor
> showed all bits as always unset.

This isn't the right fix, actually.  With split indexes, this puts us
right back into "only shows a few bits" territory, because
do_read_index doesn't know about split indexes.

Which means we need a way to do the whole index load but _not_
add/remove the fsmonitor cache, even if the config says to do so.

The best I'm coming up with is the below -- but I'm not happy with
it, because 'keep' is meaningless as a configuration value outside of
testing, since it's normally treated as an executable path.  This uses
the fact that fsmonitor.c currently has a:

        switch (fsmonitor_enabled) {
        case -1: /* keep: do nothing */
                break;

...despite get_config_get_fsmonitor() havong no way to return -1 at
present.

Is this sort of testing generally done via environment variables,
rather than magic config values?
 - Alex

---------------------8<----------------
diff --git a/config.c b/config.c
index 6fb06c213..75fcf1a52 100644
--- a/config.c
+++ b/config.c
@@ -2164,8 +2164,13 @@ int git_config_get_fsmonitor(void)
        if (core_fsmonitor && !*core_fsmonitor)
                core_fsmonitor = NULL;

-       if (core_fsmonitor)
-               return 1;
+
+       if (core_fsmonitor) {
+               if (!strcasecmp(core_fsmonitor, "keep"))
+                       return -1;
+               else
+                       return 1;
+       }

        return 0;
 }
diff --git a/t/helper/test-dump-fsmonitor.c b/t/helper/test-dump-fsmonitor.c
index ad452707e..12e131530 100644
--- a/t/helper/test-dump-fsmonitor.c
+++ b/t/helper/test-dump-fsmonitor.c
@@ -5,8 +5,9 @@ int cmd_main(int ac, const char **av)
        struct index_state *istate = &the_index;
        int i;

+       git_config_push_parameter("core.fsmonitor=keep");
        setup_git_directory();
-       if (do_read_index(istate, get_index_file(), 0) < 0)
+       if (read_index_from(istate, get_index_file()) < 0)
                die("unable to read index file");
        if (!istate->fsmonitor_last_update) {
                printf("no fsmonitor\n");
-----------------8<---------------------