Michal Privoznik <mprivozn@xxxxxxxxxx> writes:
> Some users or projects prefer different algorithms over others, e.g.
> patience over myers or similar. However, specifying appropriate
> argument every time diff is to be used is impractical. Moreover,
> creating an alias doesn't play nicely with other tools based on diff
> (git-show for instance). Hence, a configuration variable which is able
> to set specific algorithm is needed. For now, these four values are
> accepted: 'myers' (which has the same effect as not setting the config
> variable at all), 'minimal', 'patience' and 'histogram'.
>
> Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
> ---
> Documentation/diff-config.txt | 17 +++++++++++++++++
> contrib/completion/git-completion.bash | 1 +
> diff.c | 23 +++++++++++++++++++++++
> 3 files changed, 41 insertions(+)
>
> diff --git a/Documentation/diff-config.txt b/Documentation/diff-config.txt
> index 4314ad0..be31276 100644
> --- a/Documentation/diff-config.txt
> +++ b/Documentation/diff-config.txt
> @@ -155,3 +155,20 @@ diff.tool::
> "kompare". Any other value is treated as a custom diff tool,
> and there must be a corresponding `difftool.<tool>.cmd`
> option.
> +
> +diff.algorithm::
> + Choose a diff algorithm. The variants are as follows:
> ++
> +--
> +`myers`;;
> + The basic greedy diff algorithm.
> +`minimal`;;
> + Spend extra time to make sure the smallest possible diff is
> + produced.
> +`patience`;;
> + Use "patience diff" algorithm when generating patches.
> +`histogram`;;
> + This algorithm extends the patience algorithm to "support
> + low-occurrence common elements".
> +--
> ++
Sounds sensible.
> diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
> index 383518c..33e25dc 100644
> --- a/contrib/completion/git-completion.bash
> +++ b/contrib/completion/git-completion.bash
> @@ -1839,6 +1839,7 @@ _git_config ()
> diff.suppressBlankEmpty
> diff.tool
> diff.wordRegex
> + diff.algorithm
> difftool.
> difftool.prompt
> fetch.recurseSubmodules
> diff --git a/diff.c b/diff.c
> index 732d4c2..ddae5c4 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -36,6 +36,7 @@ static int diff_no_prefix;
> static int diff_stat_graph_width;
> static int diff_dirstat_permille_default = 30;
> static struct diff_options default_diff_options;
> +static long diff_algorithm = 0;
Please do not initialize a static explicitly to a zero and instead
let BSS do its thing.
> static char diff_colors[][COLOR_MAXLEN] = {
> GIT_COLOR_RESET,
> @@ -143,6 +144,20 @@ static int git_config_rename(const char *var, const char *value)
> return git_config_bool(var,value) ? DIFF_DETECT_RENAME : 0;
> }
>
> +static long parse_algorithm_value(const char *value)
> +{
> + if (!value || !strcasecmp(value, "myers"))
> + return 0;
> + else if (!strcasecmp(value, "minimal"))
> + return XDF_NEED_MINIMAL;
> + else if (!strcasecmp(value, "patience"))
> + return XDF_PATIENCE_DIFF;
> + else if (!strcasecmp(value, "histogram"))
> + return XDF_HISTOGRAM_DIFF;
> + else
> + return -1;
> +}
> +
> /*
> * These are to give UI layer defaults.
> * The core-level commands such as git-diff-files should
> @@ -196,6 +211,13 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
> return 0;
> }
>
> + if (!strcmp(var, "diff.algorithm")) {
> + diff_algorithm = parse_algorithm_value(value);
> + if (diff_algorithm < 0)
> + return -1;
> + return 0;
> + }
> +
> if (git_color_config(var, value, cb) < 0)
> return -1;
>
> @@ -3213,6 +3235,7 @@ void diff_setup(struct diff_options *options)
> options->add_remove = diff_addremove;
> options->use_color = diff_use_color_default;
> options->detect_rename = diff_detect_rename_default;
> + options->xdl_opts |= diff_algorithm;
>
> if (diff_no_prefix) {
> options->a_prefix = options->b_prefix = "";
--
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