Re: git log -S or -G

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

On Tue, Oct 09 2018, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
>
>> I think that is the best we could do for "-S", though, which is
>> inherently about counting hits.
>>
>> For "-G", we are literally grepping the diff. It does not seem
>> unreasonable to add the ability to grep only "-" or "+" lines, and the
>> interface for that should be pretty straightforward (a tri-state flag to
>> look in remove, added, or both lines).
>
> Yeah, here is a lunchtime hack that hasn't even been compile tested.
>
>  diff.c             |  4 ++++
>  diff.h             |  2 ++
>  diffcore-pickaxe.c | 22 ++++++++++++++++++++--
>  3 files changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/diff.c b/diff.c
> index f0c7557b40..d1f2780844 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -5068,6 +5068,10 @@ int diff_opt_parse(struct diff_options *options,
>  	}
>  	else if (!strcmp(arg, "--pickaxe-all"))
>  		options->pickaxe_opts |= DIFF_PICKAXE_ALL;
> +	else if (!strcmp(arg, "--pickaxe-ignore-add"))
> +		options->pickaxe_opts |= DIFF_PICKAXE_IGNORE_ADD;
> +	else if (!strcmp(arg, "--pickaxe-ignore-del"))
> +		options->pickaxe_opts |= DIFF_PICKAXE_IGNORE_DEL;
>  	else if (!strcmp(arg, "--pickaxe-regex"))
>  		options->pickaxe_opts |= DIFF_PICKAXE_REGEX;
>  	else if ((argcount = short_opt('O', av, &optarg))) {
> diff --git a/diff.h b/diff.h
> index a30cc35ec3..147c47ace7 100644
> --- a/diff.h
> +++ b/diff.h
> @@ -358,6 +358,8 @@ int git_config_rename(const char *var, const char *value);
>  				 DIFF_PICKAXE_KIND_OBJFIND)
>
>  #define DIFF_PICKAXE_IGNORE_CASE	32
> +#define DIFF_PICKAXE_IGNORE_ADD	64
> +#define DIFF_PICKAXE_IGNORE_DEL 128
>
>  void diffcore_std(struct diff_options *);
>  void diffcore_fix_diff_index(struct diff_options *);
> diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
> index 800a899c86..826dde6bd4 100644
> --- a/diffcore-pickaxe.c
> +++ b/diffcore-pickaxe.c
> @@ -16,6 +16,7 @@ typedef int (*pickaxe_fn)(mmfile_t *one, mmfile_t *two,
>
>  struct diffgrep_cb {
>  	regex_t *regexp;
> +	struct diff_options *diff_options;
>  	int hit;
>  };
>
> @@ -23,9 +24,14 @@ static void diffgrep_consume(void *priv, char *line, unsigned long len)
>  {
>  	struct diffgrep_cb *data = priv;
>  	regmatch_t regmatch;
> +	unsigned pickaxe_opts = data->diff_options->pickaxe_opts;
>
>  	if (line[0] != '+' && line[0] != '-')
>  		return;
> +	if ((pickaxe_opts & DIFF_PICKAXE_IGNORE_ADD) &&	line[0] == '+')
> +		return;
> +	if ((pickaxe_opts & DIFF_PICKAXE_IGNORE_DEL) &&	line[0] == '-')
> +		return;
>  	if (data->hit)
>  		/*

Looks good, but I wonder if a more general version of this couldn't be
that instead of returning early if the line doesn't start with +/-
above, we have an option to skip that early return.

Then you can simply specify a regex that starts by matching a + or - at
the start of the line, but you also get the poweruser tool of matching
lines around those lines, as tweaked by the -U option. I.e. this:

diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index 800a899c86..90625a110c 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -24,15 +24,13 @@ static void diffgrep_consume(void *priv, char *line, unsigned long len)
        struct diffgrep_cb *data = priv;
        regmatch_t regmatch;

-       if (line[0] != '+' && line[0] != '-')
-               return;
        if (data->hit)
                /*
                 * NEEDSWORK: we should have a way to terminate the
                 * caller early.
                 */
                return;
-       data->hit = !regexec_buf(data->regexp, line + 1, len - 1, 1,
+       data->hit = !regexec_buf(data->regexp, line, len, 1,
                                 &regmatch, 0);
 }

That patch obviously breaks existing -G, so it would need to be
optional, but allows me e.g. on git.git to do:

    ~/g/git/git --exec-path=/home/avar/g/git log -G'^ .*marc\.info' -p -U2 -- README.md

To find a change whose first line of context is a line mentioning
marc.info, and then I can use -G'^\+<rx>' to find added lines matching
<rx> etc.

Then the --pickaxe-ignore-add and --pickaxe-ignore-del options in your
patch could just be implemented in terms of that feature, i.e. by
implicitly adding a "^-" or "^\+" to the beginning of the regex,
respectively, and implicitly turning on a new --pickaxe-raw-lines or
whatever we'd call it.

>  		 * NEEDSWORK: we should have a way to terminate the
> @@ -45,13 +51,20 @@ static int diff_grep(mmfile_t *one, mmfile_t *two,
>  	xpparam_t xpp;
>  	xdemitconf_t xecfg;
>
> -	if (!one)
> +	if (!one) {
> +		if (o->pickaxe_opts & DIFF_PICKAXE_IGNORE_ADD)
> +			return 0;
>  		return !regexec_buf(regexp, two->ptr, two->size,
>  				    1, &regmatch, 0);
> -	if (!two)
> +	}
> +	if (!two) {
> +		if (o->pickaxe_opts & DIFF_PICKAXE_IGNORE_DEL)
> +			return 0;
>  		return !regexec_buf(regexp, one->ptr, one->size,
>  				    1, &regmatch, 0);
> +	}
>
> +	ecbdata.diff_options = o;
>  	/*
>  	 * We have both sides; need to run textual diff and see if
>  	 * the pattern appears on added/deleted lines.
> @@ -113,6 +126,11 @@ static int has_changes(mmfile_t *one, mmfile_t *two,
>  {
>  	unsigned int one_contains = one ? contains(one, regexp, kws) : 0;
>  	unsigned int two_contains = two ? contains(two, regexp, kws) : 0;
> +
> +	if (o->pickaxe_opts & DIFF_PICKAXE_IGNORE_ADD)
> +		return one_contains > two_contains;
> +	if (o->pickaxe_opts & DIFF_PICKAXE_IGNORE_DEL)
> +		return one_contains < two_contains;
>  	return one_contains != two_contains;
>  }
>