Re: What's cooking in git.git (Jun 2017, #06; Thu, 22)

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

On Thu, Jun 22 2017, Junio C. Hamano jotted:

> * sb/diff-color-move (2017-06-21) 25 commits
>  - diff: document the new --color-moved setting
>  - diff.c: add dimming to moved line detection
>  - diff.c: color moved lines differently, plain mode
>  - diff.c: color moved lines differently
>  - diff.c: buffer all output if asked to
>  - diff.c: emit_diff_symbol learns about DIFF_SYMBOL_SUMMARY
>  - diff.c: emit_diff_symbol learns about DIFF_SYMBOL_STAT_SEP
>  - diff.c: convert word diffing to use emit_diff_symbol
>  - diff.c: convert show_stats to use emit_diff_symbol
>  - diff.c: convert emit_binary_diff_body to use emit_diff_symbol
>  - submodule.c: migrate diff output to use emit_diff_symbol
>  - diff.c: emit_diff_symbol learns DIFF_SYMBOL_REWRITE_DIFF
>  - diff.c: emit_diff_symbol learns about DIFF_SYMBOL_BINARY_FILES
>  - diff.c: emit_diff_symbol learns DIFF_SYMBOL_HEADER
>  - diff.c: emit_diff_symbol learns DIFF_SYMBOL_FILEPAIR
>  - diff.c: emit_diff_symbol learns DIFF_SYMBOL_CONTEXT_INCOMPLETE
>  - diff.c: emit_diff_symbol learns DIFF_SYMBOL_WORDS{_PORCELAIN}
>  - diff.c: migrate emit_line_checked to use emit_diff_symbol
>  - diff.c: emit_diff_symbol learns DIFF_SYMBOL_NO_LF_EOF
>  - diff.c: emit_diff_symbol learns DIFF_SYMBOL_CONTEXT_FRAGINFO
>  - diff.c: emit_diff_symbol learns DIFF_SYMBOL_CONTEXT_MARKER
>  - diff.c: introduce emit_diff_symbol
>  - diff.c: factor out diff_flush_patch_all_file_pairs
>  - diff.c: move line ending check into emit_hunk_header
>  - diff.c: readability fix
>
>  "git diff" has been taught to optionally paint new lines that are
>  the same as deleted lines elsewhere differently from genuinely new
>  lines.
>
>  Is any more update coming?

I guess here's as good a place for feedback is any, this feature's
great, but I discovered some minor warts in it:

This is good:

    $ ./git --exec-path=$PWD show --color-moved=crap
    fatal: bad --color-moved argument: crap

This is bad:

    $ ./git --exec-path=$PWD -c diff.colorMoved=crap show
    fatal: unable to parse 'diff.colormoved' from command-line config

Fixed with:

    diff --git a/diff.c b/diff.c
    index 7cae4f1ddb..036dbc1c3c 100644
    --- a/diff.c
    +++ b/diff.c
    @@ -278,7 +278,7 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
            if (!strcmp(var, "diff.colormoved")) {
                    int cm = parse_color_moved(value);
                    if (cm < 0)
    -                       return -1;
    +                       die("bad --color-moved argument: %s", value);
                    diff_color_moved_default = cm;
                    return 0;
            }

But I'm not familiar enough with the code to say if just dying here, as
opposed to returning -1 is OK or not.

Also, I think something like this (very lighty tested) patch on top
makes sense:

    diff --git a/diff.c b/diff.c
    index 7cae4f1ddb..d195d304d3 100644
    --- a/diff.c
    +++ b/diff.c
    @@ -257,6 +257,15 @@ int git_diff_heuristic_config(const char *var, const char *value, void *cb)

     static int parse_color_moved(const char *arg)
     {
    +       int v = git_parse_maybe_bool(arg);
    +
    +       if (v != -1) {
    +               if (v == 0)
    +                       return COLOR_MOVED_NO;
    +               else if (v == 1)
    +                       return COLOR_MOVED_PLAIN;
    +       }
    +
            if (!strcmp(arg, "no"))
                    return COLOR_MOVED_NO;
            else if (!strcmp(arg, "plain"))

I don't want to set this to a specific value, just "true" and it should
pick whatever the default is (and that in the config yields a very bad
error message, hence the first patch).

If you don't want to have a default for whatever reason I think the docs
need to change:

    diff --git a/Documentation/config.txt b/Documentation/config.txt
    index 1ab7bdfb49..4b6f8c6d5c 100644
    --- a/Documentation/config.txt
    +++ b/Documentation/config.txt
    @@ -1085,8 +1085,9 @@ This does not affect linkgit:git-format-patch[1] or the
     command line with the `--color[=<when>]` option.

     diff.colorMoved::
    -       If set moved lines in a diff are colored differently,
    -       for details see '--color-moved' in linkgit:git-diff[1].
    +       If set to a valid `<mode>` moved lines in a diff are colored
    +       differently, for details of valid modes see '--color-moved' in
    +       linkgit:git-diff[1].

     color.diff.<slot>::
            Use customized color for diff colorization.  `<slot>` specifies

Right now the lazy reader (i.e. me) just reads "if set...<blah blah>"
tries it out, and then gets a cryptic error. "If set" to me immediately
sounds like a bool variable (but then I read the diff docs and found
it's not). So with that bool parsing it could be changed to:

    diff --git a/Documentation/config.txt b/Documentation/config.txt
    index 1ab7bdfb49..e62d926740 100644
    --- a/Documentation/config.txt
    +++ b/Documentation/config.txt
    @@ -1085,8 +1085,10 @@ This does not affect linkgit:git-format-patch[1] or the
     command line with the `--color[=<when>]` option.

     diff.colorMoved::
    -       If set moved lines in a diff are colored differently,
    -       for details see '--color-moved' in linkgit:git-diff[1].
    +       If set to either a valid `<mode>` or a true value, moved lines
    +       in a diff are colored differently, for details of valid modes
    +       see '--color-moved' in linkgit:git-diff[1]. If simply set to
    +       true the default color mode will be used.

     color.diff.<slot>::
            Use customized color for diff colorization.  `<slot>` specifies