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

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.

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);
+               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.

Hi,

On 03/15, Yurii Shevtsov wrote:

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.

The commit message should describe why the change is made, see
Documentation/SubmittingPatches, section (2)

Signed-off-by: Yurii Shevtsov <ungetch <at> gmail.com>

Please use your full email here, without replacing @ with <at>

---
 diff-no-index.c |   21 +++++++++++++++++++--

You should probably add a test for the new behaviour in
t/t4053-diff-no-index.sh.

This makes git diff --no-index $directory $file the same as
git diff --no-index $file $directory.  Shouldn't these commands give
different results?  (See the behaviour of diff in this case, and
compare it to the behaviour you introduced here)

+               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);
+               strbuf_release(&dirnfile);
+
+               return ret;
+       }

Your MUA seems to have replaced tabs with spaces in this email.  The
easiest way to get the formatting correct is the git send-email tool.
You should also try to sending the mail to yourself first and see if
it applies correctly with git am.

        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.
--
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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.
--