On Tue, Jul 05, 2011 at 10:41:37PM +0200, Michael Schubert wrote:
> Subject: [PATCH] help_unknown_cmd: do not propose an "unknown" cmd
>
> When executing an external shell script like `git foo` with the following
> shebang "#!/usr/bin/not/existing", execvp returns 127 (ENOENT). Since
> help_unknown_cmd proposes the use of all external commands similar to
> the name of the "unknown" command, it suggests the just failed command
> again. Stop it.
Yeah, I don't think we can distinguish "not there" versus "bad
interpreter" just from the exec return. We would have to then search the
PATH to see if the file actually exists.
> - if (SIMILAR_ENOUGH(best_similarity)) {
> + if (n==1 && !strcmp(cmd, main_cmds.names[0]->name))
> + ;
> + /*
> + * This avoids proposing the use of a command
> + * which apparently just didn't work, e.g.
> + * when executing a shell script git-foo with
> + * the following shebang:
> + *
> + * #!/usr/bin/not/here
> + *
> + */
> + else if (SIMILAR_ENOUGH(best_similarity)) {
This misses the "autocorrect" case just above, which should not
autocorrect a command to itself (and I didn't try, but I assume it makes
more a really slow infinite loop).
So if you are going to follow this strategy, you are probably better to
just skip the entry (or give it a high levenshtein distance) in the main
loop where we calculate candidates.
But I wonder if we can do even better than just omitting it from the
candidates list. I mentioned searching the PATH above; but that is
exactly what load_command_list does to create this candidate list. So I
think the only way we can have an exact match is one of:
1. There is a race condition. We tried to exec the command, and it was
missing; meanwhile, another process created the command.
2. Exec'ing the command returned ENOENT because of a bad interpreter.
Option (1) seems fairly unlikely; so maybe we should give the user some
advice about (2)?
Something like:
diff --git a/help.c b/help.c
index e925ca1..522b2ba 100644
--- a/help.c
+++ b/help.c
@@ -305,6 +305,10 @@ static void add_cmd_list(struct cmdnames *cmds, struct cmdnames *old)
#define SIMILARITY_FLOOR 7
#define SIMILAR_ENOUGH(x) ((x) < SIMILARITY_FLOOR)
+static const char bad_interpreter_advice[] =
+"'%s' appears to be a git command, but we were not able to\n"
+"execute it. Check the #!-line of the git-%s script.";
+
const char *help_unknown_cmd(const char *cmd)
{
int i, n, best_similarity = 0;
@@ -329,6 +333,14 @@ const char *help_unknown_cmd(const char *cmd)
int cmp = 0; /* avoid compiler stupidity */
const char *candidate = main_cmds.names[i]->name;
+ /*
+ * An exact match means we have the command, but
+ * for some reason exec'ing it gave us ENOENT; probably
+ * it's a bad interpreter in the #! line.
+ */
+ if (!strcmp(candidate, cmd))
+ die(bad_interpreter_advice, cmd, cmd);
+
/* Does the candidate appear in common_cmds list? */
while (n < ARRAY_SIZE(common_cmds) &&
(cmp = strcmp(common_cmds[n].name, candidate)) < 0)
I'm not all that happy with the advice, though. It's pretty technical
and specific. I'm not sure whether it would be helpful to most users or
not.
-Peff
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