Skip to content

Commit

Permalink
Merge branch 'jc/diff-algo-attribute' into jch
Browse files Browse the repository at this point in the history
* jc/diff-algo-attribute:
  diff: teach diff to read algorithm from diff driver
  diff: consolidate diff algorithm option parsing
  • Loading branch information
gitster committed Feb 21, 2023
2 parents 72c1ec2 + a4cf900 commit 14a1eb9
Show file tree
Hide file tree
Showing 6 changed files with 140 additions and 25 deletions.
31 changes: 31 additions & 0 deletions Documentation/gitattributes.txt
Expand Up @@ -758,6 +758,37 @@ with the above configuration, i.e. `j-c-diff`, with 7
parameters, just like `GIT_EXTERNAL_DIFF` program is called.
See linkgit:git[1] for details.

Setting the internal diff algorithm
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The diff algorithm can be set through the `diff.algorithm` config key, but
sometimes it may be helpful to set the diff algorithm per path. For example,
one may want to use the `minimal` diff algorithm for .json files, and the
`histogram` for .c files, and so on without having to pass in the algorithm
through the command line each time.

First, in `.gitattributes`, assign the `diff` attribute for paths.

------------------------
*.json diff=<name>
------------------------

Then, define a "diff.<name>.algorithm" configuration to specify the diff
algorithm, choosing from `myers`, `patience`, `minimal`, or `histogram`.

----------------------------------------------------------------
[diff "<name>"]
algorithm = histogram
----------------------------------------------------------------

This diff algorithm applies to user facing diff output like git-diff(1),
git-show(1) and is used for the `--stat` output as well. The merge machinery
will not use the diff algorithm set through this method.

NOTE: If `diff.<name>.command` is defined for path with the
`diff=<name>` attribute, it is executed as an external diff driver
(see above), and adding `diff.<name>.algorithm` has no effect, as the
algorithm is not passed to the external diff driver.

Defining a custom hunk-header
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand Down
90 changes: 67 additions & 23 deletions diff.c
Expand Up @@ -3437,6 +3437,22 @@ static int diff_filepair_is_phoney(struct diff_filespec *one,
return !DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two);
}

static int set_diff_algorithm(struct diff_options *opts,
const char *alg)
{
long value = parse_algorithm_value(alg);

if (value < 0)
return -1;

/* clear out previous settings */
DIFF_XDL_CLR(opts, NEED_MINIMAL);
opts->xdl_opts &= ~XDF_DIFF_ALGORITHM_MASK;
opts->xdl_opts |= value;

return 0;
}

static void builtin_diff(const char *name_a,
const char *name_b,
struct diff_filespec *one,
Expand Down Expand Up @@ -4440,15 +4456,13 @@ static void run_diff_cmd(const char *pgm,
const char *xfrm_msg = NULL;
int complete_rewrite = (p->status == DIFF_STATUS_MODIFIED) && p->score;
int must_show_header = 0;
struct userdiff_driver *drv = NULL;


if (o->flags.allow_external) {
struct userdiff_driver *drv;

if (o->flags.allow_external || !o->ignore_driver_algorithm)
drv = userdiff_find_by_path(o->repo->index, attr_path);
if (drv && drv->external)
pgm = drv->external;
}

if (o->flags.allow_external && drv && drv->external)
pgm = drv->external;

if (msg) {
/*
Expand All @@ -4465,12 +4479,16 @@ static void run_diff_cmd(const char *pgm,
run_external_diff(pgm, name, other, one, two, xfrm_msg, o);
return;
}
if (one && two)
if (one && two) {
if (!o->ignore_driver_algorithm && drv && drv->algorithm)
set_diff_algorithm(o, drv->algorithm);

builtin_diff(name, other ? other : name,
one, two, xfrm_msg, must_show_header,
o, complete_rewrite);
else
} else {
fprintf(o->file, "* Unmerged path %s\n", name);
}
}

static void diff_fill_oid_info(struct diff_filespec *one, struct index_state *istate)
Expand Down Expand Up @@ -4567,6 +4585,14 @@ static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
const char *name;
const char *other;

if (!o->ignore_driver_algorithm) {
struct userdiff_driver *drv = userdiff_find_by_path(o->repo->index,
p->one->path);

if (drv && drv->algorithm)
set_diff_algorithm(o, drv->algorithm);
}

if (DIFF_PAIR_UNMERGED(p)) {
/* unmerged */
builtin_diffstat(p->one->path, NULL, NULL, NULL,
Expand Down Expand Up @@ -5107,17 +5133,32 @@ static int diff_opt_diff_algorithm(const struct option *opt,
const char *arg, int unset)
{
struct diff_options *options = opt->value;
long value = parse_algorithm_value(arg);

BUG_ON_OPT_NEG(unset);
if (value < 0)

if (set_diff_algorithm(options, arg))
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;
options->ignore_driver_algorithm = 1;

return 0;
}

static int diff_opt_diff_algorithm_no_arg(const struct option *opt,
const char *arg, int unset)
{
struct diff_options *options = opt->value;

BUG_ON_OPT_NEG(unset);
BUG_ON_OPT_ARG(arg);

if (set_diff_algorithm(options, opt->long_name))
BUG("available diff algorithms include \"myers\", "
"\"minimal\", \"patience\" and \"histogram\"");

options->ignore_driver_algorithm = 1;

return 0;
}

Expand Down Expand Up @@ -5250,7 +5291,6 @@ static int diff_opt_patience(const struct option *opt,

BUG_ON_OPT_NEG(unset);
BUG_ON_OPT_ARG(arg);
options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
/*
* Both --patience and --anchored use PATIENCE_DIFF
* internally, so remove any anchors previously
Expand All @@ -5259,7 +5299,9 @@ static int diff_opt_patience(const struct option *opt,
for (i = 0; i < options->anchors_nr; i++)
free(options->anchors[i]);
options->anchors_nr = 0;
return 0;
options->ignore_driver_algorithm = 1;

return set_diff_algorithm(options, "patience");
}

static int diff_opt_ignore_regex(const struct option *opt,
Expand Down Expand Up @@ -5562,9 +5604,10 @@ struct option *add_diff_options(const struct option *opts,
N_("prevent rename/copy detection if the number of rename/copy targets exceeds given limit")),

OPT_GROUP(N_("Diff algorithm options")),
OPT_BIT(0, "minimal", &options->xdl_opts,
N_("produce the smallest possible diff"),
XDF_NEED_MINIMAL),
OPT_CALLBACK_F(0, "minimal", options, NULL,
N_("produce the smallest possible diff"),
PARSE_OPT_NONEG | PARSE_OPT_NOARG,
diff_opt_diff_algorithm_no_arg),
OPT_BIT_F('w', "ignore-all-space", &options->xdl_opts,
N_("ignore whitespace when comparing lines"),
XDF_IGNORE_WHITESPACE, PARSE_OPT_NONEG),
Expand All @@ -5590,9 +5633,10 @@ struct option *add_diff_options(const struct option *opts,
N_("generate diff using the \"patience diff\" algorithm"),
PARSE_OPT_NONEG | PARSE_OPT_NOARG,
diff_opt_patience),
OPT_BITOP(0, "histogram", &options->xdl_opts,
N_("generate diff using the \"histogram diff\" algorithm"),
XDF_HISTOGRAM_DIFF, XDF_DIFF_ALGORITHM_MASK),
OPT_CALLBACK_F(0, "histogram", options, NULL,
N_("generate diff using the \"histogram diff\" algorithm"),
PARSE_OPT_NONEG | PARSE_OPT_NOARG,
diff_opt_diff_algorithm_no_arg),
OPT_CALLBACK_F(0, "diff-algorithm", options, N_("<algorithm>"),
N_("choose a diff algorithm"),
PARSE_OPT_NONEG, diff_opt_diff_algorithm),
Expand Down
1 change: 1 addition & 0 deletions diff.h
Expand Up @@ -333,6 +333,7 @@ struct diff_options {
int prefix_length;
const char *stat_sep;
int xdl_opts;
int ignore_driver_algorithm;

/* see Documentation/diff-options.txt */
char **anchors;
Expand Down
38 changes: 37 additions & 1 deletion t/lib-diff-alternative.sh
Expand Up @@ -105,10 +105,46 @@ index $file1..$file2 100644
}
EOF

cat >expect_diffstat <<EOF
file1 => file2 | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)
EOF

STRATEGY=$1

test_expect_success "$STRATEGY diff from attributes" '
echo "file* diff=driver" >.gitattributes &&
git config diff.driver.algorithm "$STRATEGY" &&
test_must_fail git diff --no-index file1 file2 > output &&
cat expect &&
cat output &&
test_cmp expect output
'

test_expect_success "$STRATEGY diff from attributes has valid diffstat" '
echo "file* diff=driver" >.gitattributes &&
git config diff.driver.algorithm "$STRATEGY" &&
test_must_fail git diff --stat --no-index file1 file2 > output &&
test_cmp expect_diffstat output
'

test_expect_success "$STRATEGY diff" '
test_must_fail git diff --no-index "--$STRATEGY" file1 file2 > output &&
test_must_fail git diff --no-index "--diff-algorithm=$STRATEGY" file1 file2 > output &&
test_cmp expect output
'

test_expect_success "$STRATEGY diff command line precedence before attributes" '
echo "file* diff=driver" >.gitattributes &&
git config diff.driver.algorithm myers &&
test_must_fail git diff --no-index "--diff-algorithm=$STRATEGY" file1 file2 > output &&
test_cmp expect output
'

test_expect_success "$STRATEGY diff attributes precedence before config" '
git config diff.algorithm default &&
echo "file* diff=driver" >.gitattributes &&
git config diff.driver.algorithm "$STRATEGY" &&
test_must_fail git diff --no-index file1 file2 > output &&
test_cmp expect output
'

Expand Down
4 changes: 3 additions & 1 deletion userdiff.c
Expand Up @@ -293,7 +293,7 @@ PATTERNS("scheme",
"|([^][)(}{[ \t])+"),
PATTERNS("tex", "^(\\\\((sub)*section|chapter|part)\\*{0,1}\\{.*)$",
"\\\\[a-zA-Z@]+|\\\\.|[a-zA-Z0-9\x80-\xff]+"),
{ "default", NULL, -1, { NULL, 0 } },
{ "default", NULL, NULL, -1, { NULL, 0 } },
};
#undef PATTERNS
#undef IPATTERN
Expand Down Expand Up @@ -394,6 +394,8 @@ int userdiff_config(const char *k, const char *v)
return parse_bool(&drv->textconv_want_cache, k, v);
if (!strcmp(type, "wordregex"))
return git_config_string(&drv->word_regex, k, v);
if (!strcmp(type, "algorithm"))
return git_config_string(&drv->algorithm, k, v);

return 0;
}
Expand Down
1 change: 1 addition & 0 deletions userdiff.h
Expand Up @@ -14,6 +14,7 @@ struct userdiff_funcname {
struct userdiff_driver {
const char *name;
const char *external;
const char *algorithm;
int binary;
struct userdiff_funcname funcname;
const char *word_regex;
Expand Down

0 comments on commit 14a1eb9

Please sign in to comment.