Re: [RFC/PATCH] checkout: allow dwim for branch creation for "git checkout $branch --"

[Matthieu Moy <Matthieu.Moy@grenoble-inp.fr>]

Duy Nguyen <pclouds@gmail.com> writes:

> has_dash_dash is calculated as (argc > 1) && !strcmp(argv[1], "--"),
> so when argc == 1, the has_dash_dash must be zero, the "&&
> !has_dash_dash" is redundant.

Yes, but I'd rather not have to read the detailed definition of
has_dash_dash to understand the code. With my version, the name of the
variable is actually sufficient to understand.

> But it makes me wonder what we do with "git checkout abc def -- xyz".

Ouch. Both old and new say

$ git checkout foo bar --
error: pathspec 'foo' did not match any file(s) known to git.
error: pathspec 'bar' did not match any file(s) known to git.
error: pathspec '--' did not match any file(s) known to git.

Fortunately, this is easy to fix, by adding this on top (or before, it
doesn't matter):

commit 060cf582f5e848c5ca57231d293943a5489c5433 (HEAD, master)
Author: Matthieu Moy <Matthieu.Moy@imag.fr>
Date:   Wed Sep 25 15:41:34 2013 +0200

    checkout: proper error message on 'git checkout foo bar --'
    
    The previous code was detecting the presence of "--" by looking only at
    argument 1. As a result, "git checkout foo bar --" was interpreted as an
    ambiguous file/revision list, and errored out with:
    
    error: pathspec 'foo' did not match any file(s) known to git.
    error: pathspec 'bar' did not match any file(s) known to git.
    error: pathspec '--' did not match any file(s) known to git.
    
    This patch fixes it by walking through the argument list to find the
    "--", and now complains about the number of references given.

diff --git a/builtin/checkout.c b/builtin/checkout.c
index a5a12f6..d958d60 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -882,6 +882,7 @@ static int parse_branchname_arg(int argc, const char **argv,
        unsigned char branch_rev[20];
        const char *arg;
        int has_dash_dash;
+       int i;
 
        /*
         * case 1: git checkout <ref> -- [<paths>]
@@ -925,7 +926,15 @@ static int parse_branchname_arg(int argc, const char **argv,
                return 1;
 
        arg = argv[0];
-       has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
+       has_dash_dash = 0;
+       for (i = 0; i < argc; i++) {
+               if (!strcmp(argv[i], "--")) {
+                       has_dash_dash = i;
+                       break;
+               }
+       }
+       if (has_dash_dash >= 2)
+               die("only one reference expected, %d given.", has_dash_dash);
 
        if (!strcmp(arg, "-"))
                arg = "@{-1}";
diff --git a/t/t2010-checkout-ambiguous.sh b/t/t2010-checkout-ambiguous.sh
index 7cc0a35..2836a3e 100755
--- a/t/t2010-checkout-ambiguous.sh
+++ b/t/t2010-checkout-ambiguous.sh
@@ -47,4 +47,10 @@ test_expect_success 'disambiguate checking out from a tree-ish' '
        git diff --exit-code --quiet
 '
 
+test_expect_success 'accurate error message with more than one ref' '
+       test_must_fail git checkout HEAD master -- 2>actual &&
+       echo "fatal: only one reference expected, 2 given." >expect &&
+       test_cmp expect actual
+'
+
 test_done

I'll resend, together with tweaks to the first patch.

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/