Re: [PATCH 3/3] diff: Introduce --diff-algorithm command line option
Michal Privoznik <mprivozn@redhat.com> writes:
> Since command line options have higher priority than config file
> variables and taking previous commit into account, we need a way
> how to specify myers algorithm on command line.
Yes. We cannot stop at [2/3] without this patch.
> However,
> inventing `--myers` is not the right answer. We need far more
> general option, and that is `--diff-algorithm`.
Yes, --diff-algorithm=default would let people defeat a configured algo without knowing how exactly to spell myers.
> The older options
> (`--minimal`, `--patience` and `--histogram`) are kept for
> backward compatibility.
That is phrasing it too strongly to be acceptable.
People who do not care any configuration can keep using --histogram without having to retrain their fingers to type a much longer form you introduced (i.e. --diff-algorithm=histogram). It is and will always be just as valid a way to ask for --histogram as the new longhand is.
Show 20 quoted lines
> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
> ---
> Documentation/diff-options.txt | 22 ++++++++++++++++++++++
> contrib/completion/git-completion.bash | 11 +++++++++++
> diff.c | 12 +++++++++++-
> diff.h | 2 ++
> merge-recursive.c | 6 ++++++
> 5 files changed, 52 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
> index 39f2c50..4091f52 100644
> --- a/Documentation/diff-options.txt
> +++ b/Documentation/diff-options.txt
> @@ -45,6 +45,9 @@ ifndef::git-format-patch[]
> Synonym for `-p --raw`.
> endif::git-format-patch[]
>
> +The next three options are kept for compatibility reason. You should use the
> +`--diff-algorithm` option instead.
> +
Show 22 quoted lines
> @@ -55,6 +58,25 @@ endif::git-format-patch[]
> --histogram::
> Generate a diff using the "histogram diff" algorithm.
>
> +--diff-algorithm={patience|minimal|histogram|myers}::
> + 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".
> +--
> ++
> +You should prefer this option over the `--minimal`, `--patience` and
> +`--histogram` which are kept just for backwards compatibility.Drop the last one, and replace it with something like:
If you configured diff.algorithm to a non-default value and
want to use the default one, you have to use this form and
choose myers, i.e. --diff-algorithm=myers, as we do not have
a short-and-sweet --myers option.
(but the above is a bit too verbose, so please shorten it appropriately).
Show 99 quoted lines
> diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
> index 33e25dc..d592cf9 100644
> --- a/contrib/completion/git-completion.bash
> +++ b/contrib/completion/git-completion.bash
> @@ -1021,6 +1021,8 @@ _git_describe ()
> __gitcomp_nl "$(__git_refs)"
> }
>
> +__git_diff_algorithms="myers minimal patience histogram"
> +
> __git_diff_common_options="--stat --numstat --shortstat --summary
> --patch-with-stat --name-only --name-status --color
> --no-color --color-words --no-renames --check
> @@ -1035,6 +1037,7 @@ __git_diff_common_options="--stat --numstat --shortstat --summary
> --raw
> --dirstat --dirstat= --dirstat-by-file
> --dirstat-by-file= --cumulative
> + --diff-algorithm=
> "
>
> _git_diff ()
> @@ -1042,6 +1045,10 @@ _git_diff ()
> __git_has_doubledash && return
>
> case "$cur" in
> + --diff-algorithm=*)
> + __gitcomp "$__git_diff_algorithms" "" "${cur##--diff-algorithm=}"
> + return
> + ;;
> --*)
> __gitcomp "--cached --staged --pickaxe-all --pickaxe-regex
> --base --ours --theirs --no-index
> @@ -2114,6 +2121,10 @@ _git_show ()
> " "" "${cur#*=}"
> return
> ;;
> + --diff-algorithm=*)
> + __gitcomp "$__git_diff_algorithms" "" "${cur##--diff-algorithm=}"
> + return
> + ;;
> --*)
> __gitcomp "--pretty= --format= --abbrev-commit --oneline
> $__git_diff_common_options
> diff --git a/diff.c b/diff.c
> index ddae5c4..6418076 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -144,7 +144,7 @@ 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)
> +long parse_algorithm_value(const char *value)
> {
> if (!value || !strcasecmp(value, "myers"))
> return 0;
> @@ -3633,6 +3633,16 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
> options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
> else if (!strcmp(arg, "--histogram"))
> options->xdl_opts = DIFF_WITH_ALG(options, HISTOGRAM_DIFF);
> + else if (!prefixcmp(arg, "--diff-algorithm=")) {
> + long value = parse_algorithm_value(arg+17);
> + if (value < 0)
> + return error("option diff-algorithm accepts \"myers\", "
> + "\"minimal\", \"patience\" and \"histogram\"");
> + /* clear out previous settings */
> + DIFF_XDL_CLR(options, NEED_MINIMAL);
> + options->xdl_opts &= ~XDF_DIFF_ALGORITHM_MASK;
> + options->xdl_opts |= value;
> + }
>
> /* flags options */
> else if (!strcmp(arg, "--binary")) {
> diff --git a/diff.h b/diff.h
> index a47bae4..54c2590 100644
> --- a/diff.h
> +++ b/diff.h
> @@ -333,6 +333,8 @@ extern struct userdiff_driver *get_textconv(struct diff_filespec *one);
>
> extern int parse_rename_score(const char **cp_p);
>
> +extern long parse_algorithm_value(const char *value);
> +
> extern int print_stat_summary(FILE *fp, int files,
> int insertions, int deletions);
> extern void setup_diff_pager(struct diff_options *);
> diff --git a/merge-recursive.c b/merge-recursive.c
> index d882060..53d8feb 100644
> --- a/merge-recursive.c
> +++ b/merge-recursive.c
> @@ -2068,6 +2068,12 @@ int parse_merge_opt(struct merge_options *o, const char *s)
> o->xdl_opts = DIFF_WITH_ALG(o, PATIENCE_DIFF);
> else if (!strcmp(s, "histogram"))
> o->xdl_opts = DIFF_WITH_ALG(o, HISTOGRAM_DIFF);
> + else if (!strcmp(s, "diff-algorithm=")) {
> + long value = parse_algorithm_value(s+15);
> + if (value < 0)
> + return -1;
> + o->xdl_opts |= value;Isn't this new hunk wrong? DIFF_WITH_ALG() removes the previously chosen algorithm choice before OR'ing the new one in, so that
diff --histogram --patience
would not end up with a value PATIENCE|HISTOGRAM OR'ed together in the algo field.
Michal Privoznik