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

In addition to the points raised by Matthieu and Thomas...

On Sun, Mar 15, 2015 at 11:35 AM, Yurii Shevtsov [off-list ref] wrote:

make "git diff --no-index $directory $file" DWIM better.

Specify the area affected by the change, followed by a colon, followed
by the change summary. Drop the period at the end. So, something like:

    diff: improve '--no-index <directory> <file>' DWIMing

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.

Write in imperative mood, so "Change" rather than "Changes". By
itself, the first sentence isn't saying much; it would read better if
you combined the two sentences into one.

Is this name supposed to stand for "dir'n'file", a shorthand for
"dir-and-file"? Perhaps a simpler more idiomatic name such as "path"
would suffice. Also, you can initialize the strbuf here at point of
declaration:

    struct strbuf path = STRBUF_INIT;

+               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);

Unless this is a performance critical loop where you want to avoid
multiple re-allocations, it's customary to pass 0 for the second
argument. Doing so makes the code a bit easier to read and understand,
and avoids questions like this one: Why are you adding 2 to the
requested length? I presume that you're taking the "/" and NUL into
account, however, strbuf takes NUL into account on its own as part of
its contract, so you probably wanted to add only 1.

+               strbuf_addstr(&dirnfile, dir);
+               if (dirnfile.buf[dirnfile.len - 1] != '/')

I don't know how others feel about it, but it makes me a bit
uncomfortable to see potential access of array item -1. I suppose, in
this case, neither name will be zero-length, however, I'd still feel
more comfortable seeing that documented formally, either via assert():

    assert(dirnfile.len > 0);
    if (dirnfile.buf[dirnfile.len - 1] != '/')

or:

    if (dirnfile.len > 0 && 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);
+               strbuf_release(&dirnfile);
+
+               return ret;
+       }

        if (S_ISDIR(mode1) || S_ISDIR(mode2)) {
                struct strbuf buffer1 = STRBUF_INIT;
--

I hope I understood task correct. I think this patch requires writing
additional tests, so that's what I'm going to do now.
--