Subject: Re: [PATCH/RFC][GSoC] make "git diff --no-index $directory $file" DWIM better.

From: Junio C Hamano <[email-masked]>
Date: Sun, 15 Mar 2015 13:17:28 -0700

Yurii Shevtsov <[email-masked]> writes:

> Changes 'git diff --no-index $directory $file' behaviour.
> Now it is transformed to 'git diff --no-index $directory/&file $file'
> instead of throwing an error.

Is this asymmetric?  Shouldn't "git diff --no-index $file $directory"
behave the same way, i.e. turned into "$file $directory/$file"?

If you intended the patch to do so, perhaps

    "git diff --no-index directory/ file" used to error out, saying
    that you cannot compare a directory and a file (with the
    parameters swapped, "git diff --no-index file directory/" failed
    the same way).

    With normal "diff", "diff D/ F" acts as if it were told to
    compare D/F and F (when D/F exists---if there isn't, then it
    shows a creation of F), and behaving the same way would be more
    natural to the users.

or something?

> Signed-off-by: Yurii Shevtsov <ungetch <at> gmail.com>
> ---
>  diff-no-index.c |   21 +++++++++++++++++++--
>  1 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/diff-no-index.c b/diff-no-index.c
> index 265709b..4e71b36 100644
> --- a/diff-no-index.c
> +++ b/diff-no-index.c
> @@ -97,8 +97,25 @@ static int queue_diff(struct diff_options *o,
>         if (get_mode(name1, &mode1) || get_mode(name2, &mode2))
>                 return -1;
>
> -       if (mode1 && mode2 && S_ISDIR(mode1) != S_ISDIR(mode2))
> -               return error("file/directory conflict: %s, %s", name1, name2);
> +       if (mode1 && mode2 && S_ISDIR(mode1) != S_ISDIR(mode2)) {
> +               struct strbuf dirnfile;
> +               const char *dir, *file;
> +               char *filename;
> +               int ret = 0;
> +
> +               dir = S_ISDIR(mode1) ? name1 : name2;
> +               file = (dir == name1) ? name2 : name1;
> +               strbuf_init(&dirnfile, strlen(name1) + strlen(name2) + 2);
> +               strbuf_addstr(&dirnfile, dir);
> +               if (dirnfile.buf[dirnfile.len - 1] != '/')
> +                       strbuf_addch(&dirnfile, '/');
> +               filename = strrchr(file, '/');
> +               strbuf_addstr(&dirnfile, filename ? (filename + 1) : file);
> +               ret = queue_diff(o, dirnfile.buf, file);

Hmm, it appears that you are turning "diff F D/" into "diff D/F F",
which is the other way around here, or am I mis-reading queue_diff().

Does queue_diff() do the right thing when D/F does not exist (not a
rhetorical question; I just did not check it myself)?