Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx> writes:
> If we are given two SHA-1 and asked to determine if they are different
> (but not _what_ differences), we know right away by comparing SHA-1.
>
> A side effect of this patch is, because large files are marked binary,
> diff-tree will not need to unpack them. 'diff-index --cached' will not
> either. But 'diff-files' still does.
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx>
> ---
> diff.c | 13 +++++++++++++
> t/t1050-large.sh | 8 ++++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/diff.c b/diff.c
> index d381a6f..b85bcfb 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -2324,6 +2324,19 @@ static void builtin_diff(const char *name_a,
> } else if (!DIFF_OPT_TST(o, TEXT) &&
> ( (!textconv_one && diff_filespec_is_binary(one)) ||
> (!textconv_two && diff_filespec_is_binary(two)) )) {
> + if (!one->data && !two->data &&
> + S_ISREG(one->mode) && S_ISREG(two->mode) &&
> + !DIFF_OPT_TST(o, BINARY)) {
> + if (!hashcmp(one->sha1, two->sha1)) {
> + if (must_show_header)
> + fprintf(o->file, "%s", header.buf);
> + goto free_ab_and_return;
> + }
> + fprintf(o->file, "%s", header.buf);
> + fprintf(o->file, "%sBinary files %s and %s differ\n",
> + line_prefix, lbl[0], lbl[1]);
> + goto free_ab_and_return;
> + }
A tangent.
I think one and two can point at the same object only when this
filepair is involved in rename/copy. In other words, one and two
with the same <mode,sha1,name> would not be given to this code. And
must-show-header would be set to true long before we get here in
fill-metainfo in such a case.
I think this new code and the original below which you copied this
one from can probably be simplified. It already felt wrong to see
two copies of "fprintf(o->file "%s", header.buf)" and now we have
four of them. Because this is a copy-and-paste of the identical
logic from below, I do not want you to attempt fixing this tangent
in this patch, though.
Thanks.
> if (fill_mmfile(&mf1, one) < 0 || fill_mmfile(&mf2, two) < 0)
> die("unable to read files to diff");
> /* Quite common confusing case */
> diff --git a/t/t1050-large.sh b/t/t1050-large.sh
> index 711f22c..b294963 100755
> --- a/t/t1050-large.sh
> +++ b/t/t1050-large.sh
> @@ -116,6 +116,14 @@ test_expect_success 'diff --stat' '
> git diff --stat HEAD^ HEAD
> '
>
> +test_expect_success 'diff' '
> + git diff HEAD^ HEAD
> +'
> +
> +test_expect_success 'diff --cached' '
> + git diff --cached HEAD^
> +'
> +
> test_expect_success 'hash-object' '
> git hash-object large1
> '
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