Re: [PATCH v4] diff: add diff.srcPrefix and diff.dstPrefix configuration variables

> ---
> Changes to v3:
> - fix capitalization in the commit message
> - quotes changed to " in the diff.txt hunk (for consistency with
>   diff.mnemonicPrefix)
> - reword the diff-options.txt entry to be more explicit/definitive
> 
> Dragan: I used the lowercase `noprefix` spelling here to be consistent
> with the current state of the tree, can you please include the fix for
> this in your pending patch? Thanks.

>  Documentation/config/diff.txt  |  6 ++++++
>  Documentation/diff-options.txt |  5 +++--
>  diff.c                         | 14 ++++++++++++--
>  t/t4013-diff-various.sh        | 35 ++++++++++++++++++++++++++++++++++
>  4 files changed, 56 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/config/diff.txt 
> b/Documentation/config/diff.txt
> index 6c7e09a1ef5e..afc23d7723b6 100644
> --- a/Documentation/config/diff.txt
> +++ b/Documentation/config/diff.txt
> @@ -111,6 +111,12 @@ diff.mnemonicPrefix::
>  diff.noprefix::
>  	If set, 'git diff' does not show any source or destination prefix.
> 
> +diff.srcPrefix::
> +	If set, 'git diff' uses this source prefix. Defaults to "a/".
> +
> +diff.dstPrefix::
> +	If set, 'git diff' uses this destination prefix. Defaults to "b/".
> +
>  diff.relative::
>  	If set to 'true', 'git diff' does not show changes outside of the 
> directory
>  	and show pathnames relative to the current directory.
> diff --git a/Documentation/diff-options.txt 
> b/Documentation/diff-options.txt
> index aaaff0d46f0c..0e9456957e37 100644
> --- a/Documentation/diff-options.txt
> +++ b/Documentation/diff-options.txt
> @@ -865,8 +865,9 @@ endif::git-format-patch[]
> 
>  --default-prefix::
>  	Use the default source and destination prefixes ("a/" and "b/").
> -	This is usually the default already, but may be used to override
> -	config such as `diff.noprefix`.
> +	This overrides configuration variables such as `diff.noprefix`,
> +	`diff.srcPrefix`, `diff.dstPrefix`, and `diff.mnemonicPrefix`
> +	(see `git-config`(1)).
> 
>  --line-prefix=<prefix>::
>  	Prepend an additional prefix to every line of output.
> diff --git a/diff.c b/diff.c
> index e50def45383e..108c1875775d 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -62,6 +62,8 @@ static const char *diff_order_file_cfg;
>  int diff_auto_refresh_index = 1;
>  static int diff_mnemonic_prefix;
>  static int diff_no_prefix;
> +static const char *diff_src_prefix = "a/";
> +static const char *diff_dst_prefix = "b/";
>  static int diff_relative;
>  static int diff_stat_name_width;
>  static int diff_stat_graph_width;
> @@ -408,6 +410,12 @@ int git_diff_ui_config(const char *var, const char 
> *value,
>  		diff_no_prefix = git_config_bool(var, value);
>  		return 0;
>  	}
> +	if (!strcmp(var, "diff.srcprefix")) {
> +		return git_config_string(&diff_src_prefix, var, value);
> +	}
> +	if (!strcmp(var, "diff.dstprefix")) {
> +		return git_config_string(&diff_dst_prefix, var, value);
> +	}
>  	if (!strcmp(var, "diff.relative")) {
>  		diff_relative = git_config_bool(var, value);
>  		return 0;
> @@ -3425,8 +3433,8 @@ void diff_set_noprefix(struct diff_options 
> *options)
> 
>  void diff_set_default_prefix(struct diff_options *options)
>  {
> -	options->a_prefix = "a/";
> -	options->b_prefix = "b/";
> +	options->a_prefix = diff_src_prefix;
> +	options->b_prefix = diff_dst_prefix;
>  }
> 
>  struct userdiff_driver *get_textconv(struct repository *r,
> @@ -5362,6 +5370,8 @@ static int diff_opt_default_prefix(const struct
> option *opt,
> 
>  	BUG_ON_OPT_NEG(unset);
>  	BUG_ON_OPT_ARG(optarg);
> +	diff_src_prefix = "a/";
> +	diff_dst_prefix = "b/";
>  	diff_set_default_prefix(options);
>  	return 0;
>  }
> diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
> index 1e3b2dbea484..e75f9f7d4cb2 100755
> --- a/t/t4013-diff-various.sh
> +++ b/t/t4013-diff-various.sh
> @@ -663,6 +663,41 @@ test_expect_success 'diff --default-prefix
> overrides diff.mnemonicprefix' '
>  	check_prefix actual a/file0 b/file0
>  '
> 
> +test_expect_success 'diff respects diff.srcprefix' '
> +	git -c diff.srcprefix=x/ diff >actual &&
> +	check_prefix actual x/file0 b/file0
> +'
> +
> +test_expect_success 'diff respects diff.dstprefix' '
> +	git -c diff.dstprefix=y/ diff >actual &&
> +	check_prefix actual a/file0 y/file0
> +'
> +
> +test_expect_success 'diff --src-prefix overrides diff.srcprefix' '
> +	git -c diff.srcprefix=z/ diff --src-prefix=z/ >actual &&

> +	check_prefix actual z/file0 b/file0
> +'
> +
> +test_expect_success 'diff --dst-prefix overrides diff.dstprefix' '
> +	git -c diff.dstprefix=y/ diff --dst-prefix=z/ >actual &&
> +	check_prefix actual a/file0 z/file0
> +'
> +
> +test_expect_success 'diff src/dstprefix ignored with diff.noprefix' '

> +	git -c diff.dstprefix=y/ -c diff.srcprefix=x/ -c diff.noprefix diff 
> >actual &&
> +	check_prefix actual file0 file0
> +'
> +
> +test_expect_success 'diff src/dstprefix ignored with 
> diff.mnemonicprefix' '

> +	git -c diff.dstprefix=x/ -c diff.srcprefix=y/ -c diff.mnemonicprefix
> diff >actual &&
> +	check_prefix actual i/file0 w/file0
> +'
> +
> +test_expect_success 'diff src/dstprefix ignored with --default-prefix' 
> '

> +	git -c diff.dstprefix=x/ -c diff.srcprefix=y/ diff --default-prefix 
> >actual &&
> +	check_prefix actual a/file0 b/file0
> +'
> +
>  test_expect_success 'diff --no-renames cannot be abbreviated' '
>  	test_expect_code 129 git diff --no-rename >actual 2>error &&
>  	test_must_be_empty actual &&