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authorJunio C Hamano <gitster@pobox.com>2016-09-26 23:09:16 (GMT)
committerJunio C Hamano <gitster@pobox.com>2016-09-26 23:09:16 (GMT)
commitb7af6ae5cff8439fdf5b72f926cab2e614906af3 (patch)
treebc9721ce62fa88e4c2824e04069380d40e09d2d9
parentb3e588a48af0ce15832c240887b9a3f9361d22bb (diff)
parent5b162879e93dab3b4bcd66afdbea3a96660abd7d (diff)
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Merge branch 'mh/diff-indent-heuristic'
Output from "git diff" can be made easier to read by selecting which lines are common and which lines are added/deleted intelligently when the lines before and after the changed section are the same. A command line option is added to help with the experiment to find a good heuristics. * mh/diff-indent-heuristic: blame: honor the diff heuristic options and config parse-options: add parse_opt_unknown_cb() diff: improve positioning of add/delete blocks in diffs xdl_change_compact(): introduce the concept of a change group recs_match(): take two xrecord_t pointers as arguments is_blank_line(): take a single xrecord_t as argument xdl_change_compact(): only use heuristic if group can't be matched xdl_change_compact(): fix compaction heuristic to adjust ixo
-rw-r--r--Documentation/diff-config.txt7
-rw-r--r--Documentation/diff-heuristic-options.txt7
-rw-r--r--Documentation/diff-options.txt7
-rw-r--r--Documentation/git-annotate.txt1
-rw-r--r--Documentation/git-blame.txt2
-rw-r--r--builtin/blame.c12
-rw-r--r--diff.c36
-rw-r--r--diff.h1
-rwxr-xr-xgit-add--interactive.perl5
-rw-r--r--parse-options-cb.c12
-rw-r--r--parse-options.h1
-rwxr-xr-xt/t4061-diff-indent.sh216
-rw-r--r--xdiff/xdiff.h1
-rw-r--r--xdiff/xdiffi.c635
14 files changed, 828 insertions, 115 deletions
diff --git a/Documentation/diff-config.txt b/Documentation/diff-config.txt
index 0eded24..b27a38f 100644
--- a/Documentation/diff-config.txt
+++ b/Documentation/diff-config.txt
@@ -171,10 +171,11 @@ diff.tool::
include::mergetools-diff.txt[]
+diff.indentHeuristic::
diff.compactionHeuristic::
- Set this option to `true` to enable an experimental heuristic that
- shifts the hunk boundary in an attempt to make the resulting
- patch easier to read.
+ Set one of these options to `true` to enable one of two
+ experimental heuristics that shift diff hunk boundaries to
+ make patches easier to read.
diff.algorithm::
Choose a diff algorithm. The variants are as follows:
diff --git a/Documentation/diff-heuristic-options.txt b/Documentation/diff-heuristic-options.txt
new file mode 100644
index 0000000..36cb549
--- /dev/null
+++ b/Documentation/diff-heuristic-options.txt
@@ -0,0 +1,7 @@
+--indent-heuristic::
+--no-indent-heuristic::
+--compaction-heuristic::
+--no-compaction-heuristic::
+ These are to help debugging and tuning experimental heuristics
+ (which are off by default) that shift diff hunk boundaries to
+ make patches easier to read.
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 7805a0c..2d77a19 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -63,12 +63,7 @@ ifndef::git-format-patch[]
Synonym for `-p --raw`.
endif::git-format-patch[]
---compaction-heuristic::
---no-compaction-heuristic::
- These are to help debugging and tuning an experimental
- heuristic (which is off by default) that shifts the hunk
- boundary in an attempt to make the resulting patch easier
- to read.
+include::diff-heuristic-options.txt[]
--minimal::
Spend extra time to make sure the smallest possible
diff --git a/Documentation/git-annotate.txt b/Documentation/git-annotate.txt
index 05fd482..94be4b8 100644
--- a/Documentation/git-annotate.txt
+++ b/Documentation/git-annotate.txt
@@ -23,6 +23,7 @@ familiar command name for people coming from other SCM systems.
OPTIONS
-------
include::blame-options.txt[]
+include::diff-heuristic-options.txt[]
SEE ALSO
--------
diff --git a/Documentation/git-blame.txt b/Documentation/git-blame.txt
index ba54175..9dccb33 100644
--- a/Documentation/git-blame.txt
+++ b/Documentation/git-blame.txt
@@ -89,6 +89,8 @@ include::blame-options.txt[]
abbreviated object name, use <n>+1 digits. Note that 1 column
is used for a caret to mark the boundary commit.
+include::diff-heuristic-options.txt[]
+
THE PORCELAIN FORMAT
--------------------
diff --git a/builtin/blame.c b/builtin/blame.c
index 2ff18b1..a7bd7a6 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -2220,6 +2220,8 @@ static int git_blame_config(const char *var, const char *value, void *cb)
return 0;
}
+ if (git_diff_heuristic_config(var, value, cb) < 0)
+ return -1;
if (userdiff_config(var, value) < 0)
return -1;
@@ -2550,6 +2552,15 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
OPT_BIT('s', NULL, &output_option, N_("Suppress author name and timestamp (Default: off)"), OUTPUT_NO_AUTHOR),
OPT_BIT('e', "show-email", &output_option, N_("Show author email instead of name (Default: off)"), OUTPUT_SHOW_EMAIL),
OPT_BIT('w', NULL, &xdl_opts, N_("Ignore whitespace differences"), XDF_IGNORE_WHITESPACE),
+
+ /*
+ * The following two options are parsed by parse_revision_opt()
+ * and are only included here to get included in the "-h"
+ * output:
+ */
+ { OPTION_LOWLEVEL_CALLBACK, 0, "indent-heuristic", NULL, NULL, N_("Use an experimental indent-based heuristic to improve diffs"), PARSE_OPT_NOARG, parse_opt_unknown_cb },
+ { OPTION_LOWLEVEL_CALLBACK, 0, "compaction-heuristic", NULL, NULL, N_("Use an experimental blank-line-based heuristic to improve diffs"), PARSE_OPT_NOARG, parse_opt_unknown_cb },
+
OPT_BIT(0, "minimal", &xdl_opts, N_("Spend extra cycles to find better match"), XDF_NEED_MINIMAL),
OPT_STRING('S', NULL, &revs_file, N_("file"), N_("Use revisions from <file> instead of calling git-rev-list")),
OPT_STRING(0, "contents", &contents_from, N_("file"), N_("Use <file>'s contents as the final image")),
@@ -2596,6 +2607,7 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
}
parse_done:
no_whole_file_rename = !DIFF_OPT_TST(&revs.diffopt, FOLLOW_RENAMES);
+ xdl_opts |= revs.diffopt.xdl_opts & (XDF_COMPACTION_HEURISTIC | XDF_INDENT_HEURISTIC);
DIFF_OPT_CLR(&revs.diffopt, FOLLOW_RENAMES);
argc = parse_options_end(&ctx);
diff --git a/diff.c b/diff.c
index c6da383..dc5ab8b 100644
--- a/diff.c
+++ b/diff.c
@@ -27,6 +27,7 @@
#endif
static int diff_detect_rename_default;
+static int diff_indent_heuristic; /* experimental */
static int diff_compaction_heuristic; /* experimental */
static int diff_rename_limit_default = 400;
static int diff_suppress_blank_empty;
@@ -177,6 +178,21 @@ void init_diff_ui_defaults(void)
diff_detect_rename_default = 1;
}
+int git_diff_heuristic_config(const char *var, const char *value, void *cb)
+{
+ if (!strcmp(var, "diff.indentheuristic")) {
+ diff_indent_heuristic = git_config_bool(var, value);
+ if (diff_indent_heuristic)
+ diff_compaction_heuristic = 0;
+ }
+ if (!strcmp(var, "diff.compactionheuristic")) {
+ diff_compaction_heuristic = git_config_bool(var, value);
+ if (diff_compaction_heuristic)
+ diff_indent_heuristic = 0;
+ }
+ return 0;
+}
+
int git_diff_ui_config(const char *var, const char *value, void *cb)
{
if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff")) {
@@ -193,10 +209,6 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
diff_detect_rename_default = git_config_rename(var, value);
return 0;
}
- if (!strcmp(var, "diff.compactionheuristic")) {
- diff_compaction_heuristic = git_config_bool(var, value);
- return 0;
- }
if (!strcmp(var, "diff.autorefreshindex")) {
diff_auto_refresh_index = git_config_bool(var, value);
return 0;
@@ -237,6 +249,8 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
return 0;
}
+ if (git_diff_heuristic_config(var, value, cb) < 0)
+ return -1;
if (git_color_config(var, value, cb) < 0)
return -1;
@@ -3296,7 +3310,9 @@ void diff_setup(struct diff_options *options)
options->use_color = diff_use_color_default;
options->detect_rename = diff_detect_rename_default;
options->xdl_opts |= diff_algorithm;
- if (diff_compaction_heuristic)
+ if (diff_indent_heuristic)
+ DIFF_XDL_SET(options, INDENT_HEURISTIC);
+ else if (diff_compaction_heuristic)
DIFF_XDL_SET(options, COMPACTION_HEURISTIC);
options->orderfile = diff_order_file_cfg;
@@ -3818,9 +3834,15 @@ int diff_opt_parse(struct diff_options *options,
DIFF_XDL_SET(options, IGNORE_WHITESPACE_AT_EOL);
else if (!strcmp(arg, "--ignore-blank-lines"))
DIFF_XDL_SET(options, IGNORE_BLANK_LINES);
- else if (!strcmp(arg, "--compaction-heuristic"))
+ else if (!strcmp(arg, "--indent-heuristic")) {
+ DIFF_XDL_SET(options, INDENT_HEURISTIC);
+ DIFF_XDL_CLR(options, COMPACTION_HEURISTIC);
+ } else if (!strcmp(arg, "--no-indent-heuristic"))
+ DIFF_XDL_CLR(options, INDENT_HEURISTIC);
+ else if (!strcmp(arg, "--compaction-heuristic")) {
DIFF_XDL_SET(options, COMPACTION_HEURISTIC);
- else if (!strcmp(arg, "--no-compaction-heuristic"))
+ DIFF_XDL_CLR(options, INDENT_HEURISTIC);
+ } else if (!strcmp(arg, "--no-compaction-heuristic"))
DIFF_XDL_CLR(options, COMPACTION_HEURISTIC);
else if (!strcmp(arg, "--patience"))
options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
diff --git a/diff.h b/diff.h
index ec76a90..25ae60d 100644
--- a/diff.h
+++ b/diff.h
@@ -273,6 +273,7 @@ extern int parse_long_opt(const char *opt, const char **argv,
const char **optarg);
extern int git_diff_basic_config(const char *var, const char *value, void *cb);
+extern int git_diff_heuristic_config(const char *var, const char *value, void *cb);
extern void init_diff_ui_defaults(void);
extern int git_diff_ui_config(const char *var, const char *value, void *cb);
extern void diff_setup(struct diff_options *);
diff --git a/git-add--interactive.perl b/git-add--interactive.perl
index 642cce1..ee3d812 100755
--- a/git-add--interactive.perl
+++ b/git-add--interactive.perl
@@ -45,6 +45,7 @@ my ($diff_new_color) =
my $normal_color = $repo->get_color("", "reset");
my $diff_algorithm = $repo->config('diff.algorithm');
+my $diff_indent_heuristic = $repo->config_bool('diff.indentheuristic');
my $diff_compaction_heuristic = $repo->config_bool('diff.compactionheuristic');
my $diff_filter = $repo->config('interactive.difffilter');
@@ -750,7 +751,9 @@ sub parse_diff {
if (defined $diff_algorithm) {
splice @diff_cmd, 1, 0, "--diff-algorithm=${diff_algorithm}";
}
- if ($diff_compaction_heuristic) {
+ if ($diff_indent_heuristic) {
+ splice @diff_cmd, 1, 0, "--indent-heuristic";
+ } elsif ($diff_compaction_heuristic) {
splice @diff_cmd, 1, 0, "--compaction-heuristic";
}
if (defined $patch_mode_revision) {
diff --git a/parse-options-cb.c b/parse-options-cb.c
index 9667bc7..b5d9209 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -159,6 +159,18 @@ int parse_opt_noop_cb(const struct option *opt, const char *arg, int unset)
}
/**
+ * Report that the option is unknown, so that other code can handle
+ * it. This can be used as a callback together with
+ * OPTION_LOWLEVEL_CALLBACK to allow an option to be documented in the
+ * "-h" output even if it's not being handled directly by
+ * parse_options().
+ */
+int parse_opt_unknown_cb(const struct option *opt, const char *arg, int unset)
+{
+ return -2;
+}
+
+/**
* Recreates the command-line option in the strbuf.
*/
static int recreate_opt(struct strbuf *sb, const struct option *opt,
diff --git a/parse-options.h b/parse-options.h
index 78f8384..dcd8a09 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -228,6 +228,7 @@ extern int parse_opt_commits(const struct option *, const char *, int);
extern int parse_opt_tertiary(const struct option *, const char *, int);
extern int parse_opt_string_list(const struct option *, const char *, int);
extern int parse_opt_noop_cb(const struct option *, const char *, int);
+extern int parse_opt_unknown_cb(const struct option *, const char *, int);
extern int parse_opt_passthru(const struct option *, const char *, int);
extern int parse_opt_passthru_argv(const struct option *, const char *, int);
diff --git a/t/t4061-diff-indent.sh b/t/t4061-diff-indent.sh
new file mode 100755
index 0000000..5564506
--- /dev/null
+++ b/t/t4061-diff-indent.sh
@@ -0,0 +1,216 @@
+#!/bin/sh
+
+test_description='Test diff indent heuristic.
+
+'
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/diff-lib.sh
+
+# Compare two diff outputs. Ignore "index" lines, because we don't
+# care about SHA-1s or file modes.
+compare_diff () {
+ sed -e "/^index /d" <"$1" >.tmp-1
+ sed -e "/^index /d" <"$2" >.tmp-2
+ test_cmp .tmp-1 .tmp-2 && rm -f .tmp-1 .tmp-2
+}
+
+# Compare blame output using the expectation for a diff as reference.
+# Only look for the lines coming from non-boundary commits.
+compare_blame () {
+ sed -n -e "1,4d" -e "s/^\+//p" <"$1" >.tmp-1
+ sed -ne "s/^[^^][^)]*) *//p" <"$2" >.tmp-2
+ test_cmp .tmp-1 .tmp-2 && rm -f .tmp-1 .tmp-2
+}
+
+test_expect_success 'prepare' '
+ cat <<-\EOF >spaces.txt &&
+ 1
+ 2
+ a
+
+ b
+ 3
+ 4
+ EOF
+
+ cat <<-\EOF >functions.c &&
+ 1
+ 2
+ /* function */
+ foo() {
+ foo
+ }
+
+ 3
+ 4
+ EOF
+
+ git add spaces.txt functions.c &&
+ test_tick &&
+ git commit -m initial &&
+ git branch old &&
+
+ cat <<-\EOF >spaces.txt &&
+ 1
+ 2
+ a
+
+ b
+ a
+
+ b
+ 3
+ 4
+ EOF
+
+ cat <<-\EOF >functions.c &&
+ 1
+ 2
+ /* function */
+ bar() {
+ foo
+ }
+
+ /* function */
+ foo() {
+ foo
+ }
+
+ 3
+ 4
+ EOF
+
+ git add spaces.txt functions.c &&
+ test_tick &&
+ git commit -m initial &&
+ git branch new &&
+
+ tr "_" " " <<-\EOF >spaces-expect &&
+ diff --git a/spaces.txt b/spaces.txt
+ --- a/spaces.txt
+ +++ b/spaces.txt
+ @@ -3,5 +3,8 @@
+ a
+ _
+ b
+ +a
+ +
+ +b
+ 3
+ 4
+ EOF
+
+ tr "_" " " <<-\EOF >spaces-compacted-expect &&
+ diff --git a/spaces.txt b/spaces.txt
+ --- a/spaces.txt
+ +++ b/spaces.txt
+ @@ -2,6 +2,9 @@
+ 2
+ a
+ _
+ +b
+ +a
+ +
+ b
+ 3
+ 4
+ EOF
+
+ tr "_" " " <<-\EOF >functions-expect &&
+ diff --git a/functions.c b/functions.c
+ --- a/functions.c
+ +++ b/functions.c
+ @@ -1,6 +1,11 @@
+ 1
+ 2
+ /* function */
+ +bar() {
+ + foo
+ +}
+ +
+ +/* function */
+ foo() {
+ foo
+ }
+ EOF
+
+ tr "_" " " <<-\EOF >functions-compacted-expect
+ diff --git a/functions.c b/functions.c
+ --- a/functions.c
+ +++ b/functions.c
+ @@ -1,5 +1,10 @@
+ 1
+ 2
+ +/* function */
+ +bar() {
+ + foo
+ +}
+ +
+ /* function */
+ foo() {
+ foo
+ EOF
+'
+
+test_expect_success 'diff: ugly spaces' '
+ git diff old new -- spaces.txt >out &&
+ compare_diff spaces-expect out
+'
+
+test_expect_success 'diff: nice spaces with --indent-heuristic' '
+ git diff --indent-heuristic old new -- spaces.txt >out-compacted &&
+ compare_diff spaces-compacted-expect out-compacted
+'
+
+test_expect_success 'diff: nice spaces with diff.indentHeuristic' '
+ git -c diff.indentHeuristic=true diff old new -- spaces.txt >out-compacted2 &&
+ compare_diff spaces-compacted-expect out-compacted2
+'
+
+test_expect_success 'diff: --no-indent-heuristic overrides config' '
+ git -c diff.indentHeuristic=true diff --no-indent-heuristic old new -- spaces.txt >out2 &&
+ compare_diff spaces-expect out2
+'
+
+test_expect_success 'diff: --indent-heuristic with --patience' '
+ git diff --indent-heuristic --patience old new -- spaces.txt >out-compacted3 &&
+ compare_diff spaces-compacted-expect out-compacted3
+'
+
+test_expect_success 'diff: --indent-heuristic with --histogram' '
+ git diff --indent-heuristic --histogram old new -- spaces.txt >out-compacted4 &&
+ compare_diff spaces-compacted-expect out-compacted4
+'
+
+test_expect_success 'diff: ugly functions' '
+ git diff old new -- functions.c >out &&
+ compare_diff functions-expect out
+'
+
+test_expect_success 'diff: nice functions with --indent-heuristic' '
+ git diff --indent-heuristic old new -- functions.c >out-compacted &&
+ compare_diff functions-compacted-expect out-compacted
+'
+
+test_expect_success 'blame: ugly spaces' '
+ git blame old..new -- spaces.txt >out-blame &&
+ compare_blame spaces-expect out-blame
+'
+
+test_expect_success 'blame: nice spaces with --indent-heuristic' '
+ git blame --indent-heuristic old..new -- spaces.txt >out-blame-compacted &&
+ compare_blame spaces-compacted-expect out-blame-compacted
+'
+
+test_expect_success 'blame: nice spaces with diff.indentHeuristic' '
+ git -c diff.indentHeuristic=true blame old..new -- spaces.txt >out-blame-compacted2 &&
+ compare_blame spaces-compacted-expect out-blame-compacted2
+'
+
+test_expect_success 'blame: --no-indent-heuristic overrides config' '
+ git -c diff.indentHeuristic=true blame --no-indent-heuristic old..new -- spaces.txt >out-blame2 &&
+ git blame old..new -- spaces.txt >out-blame &&
+ compare_blame spaces-expect out-blame2
+'
+
+test_done
diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index 7423f77..8db16d4 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -42,6 +42,7 @@ extern "C" {
#define XDF_IGNORE_BLANK_LINES (1 << 7)
#define XDF_COMPACTION_HEURISTIC (1 << 8)
+#define XDF_INDENT_HEURISTIC (1 << 9)
#define XDL_EMIT_FUNCNAMES (1 << 0)
#define XDL_EMIT_FUNCCONTEXT (1 << 2)
diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index b3c6848..67c1ccc 100644
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -400,138 +400,577 @@ static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1,
}
-static int is_blank_line(xrecord_t **recs, long ix, long flags)
+static int is_blank_line(xrecord_t *rec, long flags)
{
- return xdl_blankline(recs[ix]->ptr, recs[ix]->size, flags);
+ return xdl_blankline(rec->ptr, rec->size, flags);
}
-static int recs_match(xrecord_t **recs, long ixs, long ix, long flags)
+static int recs_match(xrecord_t *rec1, xrecord_t *rec2, long flags)
{
- return (recs[ixs]->ha == recs[ix]->ha &&
- xdl_recmatch(recs[ixs]->ptr, recs[ixs]->size,
- recs[ix]->ptr, recs[ix]->size,
+ return (rec1->ha == rec2->ha &&
+ xdl_recmatch(rec1->ptr, rec1->size,
+ rec2->ptr, rec2->size,
flags));
}
-int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
- long ix, ixo, ixs, ixref, grpsiz, nrec = xdf->nrec;
- char *rchg = xdf->rchg, *rchgo = xdfo->rchg;
- unsigned int blank_lines;
- xrecord_t **recs = xdf->recs;
+/*
+ * If a line is indented more than this, get_indent() just returns this value.
+ * This avoids having to do absurd amounts of work for data that are not
+ * human-readable text, and also ensures that the output of get_indent fits within
+ * an int.
+ */
+#define MAX_INDENT 200
+/*
+ * Return the amount of indentation of the specified line, treating TAB as 8
+ * columns. Return -1 if line is empty or contains only whitespace. Clamp the
+ * output value at MAX_INDENT.
+ */
+static int get_indent(xrecord_t *rec)
+{
+ long i;
+ int ret = 0;
+
+ for (i = 0; i < rec->size; i++) {
+ char c = rec->ptr[i];
+
+ if (!XDL_ISSPACE(c))
+ return ret;
+ else if (c == ' ')
+ ret += 1;
+ else if (c == '\t')
+ ret += 8 - ret % 8;
+ /* ignore other whitespace characters */
+
+ if (ret >= MAX_INDENT)
+ return MAX_INDENT;
+ }
+
+ /* The line contains only whitespace. */
+ return -1;
+}
+
+/*
+ * If more than this number of consecutive blank rows are found, just return this
+ * value. This avoids requiring O(N^2) work for pathological cases, and also
+ * ensures that the output of score_split fits in an int.
+ */
+#define MAX_BLANKS 20
+
+/* Characteristics measured about a hypothetical split position. */
+struct split_measurement {
/*
- * This is the same of what GNU diff does. Move back and forward
- * change groups for a consistent and pretty diff output. This also
- * helps in finding joinable change groups and reduce the diff size.
+ * Is the split at the end of the file (aside from any blank lines)?
*/
- for (ix = ixo = 0;;) {
- /*
- * Find the first changed line in the to-be-compacted file.
- * We need to keep track of both indexes, so if we find a
- * changed lines group on the other file, while scanning the
- * to-be-compacted file, we need to skip it properly. Note
- * that loops that are testing for changed lines on rchg* do
- * not need index bounding since the array is prepared with
- * a zero at position -1 and N.
- */
- for (; ix < nrec && !rchg[ix]; ix++)
- while (rchgo[ixo++]);
- if (ix == nrec)
+ int end_of_file;
+
+ /*
+ * How much is the line immediately following the split indented (or -1 if
+ * the line is blank):
+ */
+ int indent;
+
+ /*
+ * How many consecutive lines above the split are blank?
+ */
+ int pre_blank;
+
+ /*
+ * How much is the nearest non-blank line above the split indented (or -1
+ * if there is no such line)?
+ */
+ int pre_indent;
+
+ /*
+ * How many lines after the line following the split are blank?
+ */
+ int post_blank;
+
+ /*
+ * How much is the nearest non-blank line after the line following the
+ * split indented (or -1 if there is no such line)?
+ */
+ int post_indent;
+};
+
+struct split_score {
+ /* The effective indent of this split (smaller is preferred). */
+ int effective_indent;
+
+ /* Penalty for this split (smaller is preferred). */
+ int penalty;
+};
+
+/*
+ * Fill m with information about a hypothetical split of xdf above line split.
+ */
+static void measure_split(const xdfile_t *xdf, long split,
+ struct split_measurement *m)
+{
+ long i;
+
+ if (split >= xdf->nrec) {
+ m->end_of_file = 1;
+ m->indent = -1;
+ } else {
+ m->end_of_file = 0;
+ m->indent = get_indent(xdf->recs[split]);
+ }
+
+ m->pre_blank = 0;
+ m->pre_indent = -1;
+ for (i = split - 1; i >= 0; i--) {
+ m->pre_indent = get_indent(xdf->recs[i]);
+ if (m->pre_indent != -1)
+ break;
+ m->pre_blank += 1;
+ if (m->pre_blank == MAX_BLANKS) {
+ m->pre_indent = 0;
+ break;
+ }
+ }
+
+ m->post_blank = 0;
+ m->post_indent = -1;
+ for (i = split + 1; i < xdf->nrec; i++) {
+ m->post_indent = get_indent(xdf->recs[i]);
+ if (m->post_indent != -1)
break;
+ m->post_blank += 1;
+ if (m->post_blank == MAX_BLANKS) {
+ m->post_indent = 0;
+ break;
+ }
+ }
+}
+
+/*
+ * The empirically-determined weight factors used by score_split() below.
+ * Larger values means that the position is a less favorable place to split.
+ *
+ * Note that scores are only ever compared against each other, so multiplying
+ * all of these weight/penalty values by the same factor wouldn't change the
+ * heuristic's behavior. Still, we need to set that arbitrary scale *somehow*.
+ * In practice, these numbers are chosen to be large enough that they can be
+ * adjusted relative to each other with sufficient precision despite using
+ * integer math.
+ */
+
+/* Penalty if there are no non-blank lines before the split */
+#define START_OF_FILE_PENALTY 1
+
+/* Penalty if there are no non-blank lines after the split */
+#define END_OF_FILE_PENALTY 21
+/* Multiplier for the number of blank lines around the split */
+#define TOTAL_BLANK_WEIGHT (-30)
+
+/* Multiplier for the number of blank lines after the split */
+#define POST_BLANK_WEIGHT 6
+
+/*
+ * Penalties applied if the line is indented more than its predecessor
+ */
+#define RELATIVE_INDENT_PENALTY (-4)
+#define RELATIVE_INDENT_WITH_BLANK_PENALTY 10
+
+/*
+ * Penalties applied if the line is indented less than both its predecessor and
+ * its successor
+ */
+#define RELATIVE_OUTDENT_PENALTY 24
+#define RELATIVE_OUTDENT_WITH_BLANK_PENALTY 17
+
+/*
+ * Penalties applied if the line is indented less than its predecessor but not
+ * less than its successor
+ */
+#define RELATIVE_DEDENT_PENALTY 23
+#define RELATIVE_DEDENT_WITH_BLANK_PENALTY 17
+
+/*
+ * We only consider whether the sum of the effective indents for splits are
+ * less than (-1), equal to (0), or greater than (+1) each other. The resulting
+ * value is multiplied by the following weight and combined with the penalty to
+ * determine the better of two scores.
+ */
+#define INDENT_WEIGHT 60
+
+/*
+ * Compute a badness score for the hypothetical split whose measurements are
+ * stored in m. The weight factors were determined empirically using the tools and
+ * corpus described in
+ *
+ * https://github.com/mhagger/diff-slider-tools
+ *
+ * Also see that project if you want to improve the weights based on, for example,
+ * a larger or more diverse corpus.
+ */
+static void score_add_split(const struct split_measurement *m, struct split_score *s)
+{
+ /*
+ * A place to accumulate penalty factors (positive makes this index more
+ * favored):
+ */
+ int post_blank, total_blank, indent, any_blanks;
+
+ if (m->pre_indent == -1 && m->pre_blank == 0)
+ s->penalty += START_OF_FILE_PENALTY;
+
+ if (m->end_of_file)
+ s->penalty += END_OF_FILE_PENALTY;
+
+ /*
+ * Set post_blank to the number of blank lines following the split,
+ * including the line immediately after the split:
+ */
+ post_blank = (m->indent == -1) ? 1 + m->post_blank : 0;
+ total_blank = m->pre_blank + post_blank;
+
+ /* Penalties based on nearby blank lines: */
+ s->penalty += TOTAL_BLANK_WEIGHT * total_blank;
+ s->penalty += POST_BLANK_WEIGHT * post_blank;
+
+ if (m->indent != -1)
+ indent = m->indent;
+ else
+ indent = m->post_indent;
+
+ any_blanks = (total_blank != 0);
+
+ /* Note that the effective indent is -1 at the end of the file: */
+ s->effective_indent += indent;
+
+ if (indent == -1) {
+ /* No additional adjustments needed. */
+ } else if (m->pre_indent == -1) {
+ /* No additional adjustments needed. */
+ } else if (indent > m->pre_indent) {
+ /*
+ * The line is indented more than its predecessor.
+ */
+ s->penalty += any_blanks ?
+ RELATIVE_INDENT_WITH_BLANK_PENALTY :
+ RELATIVE_INDENT_PENALTY;
+ } else if (indent == m->pre_indent) {
+ /*
+ * The line has the same indentation level as its predecessor.
+ * No additional adjustments needed.
+ */
+ } else {
/*
- * Record the start of a changed-group in the to-be-compacted file
- * and find the end of it, on both to-be-compacted and other file
- * indexes (ix and ixo).
+ * The line is indented less than its predecessor. It could be
+ * the block terminator of the previous block, but it could
+ * also be the start of a new block (e.g., an "else" block, or
+ * maybe the previous block didn't have a block terminator).
+ * Try to distinguish those cases based on what comes next:
*/
- ixs = ix;
- for (ix++; rchg[ix]; ix++);
- for (; rchgo[ixo]; ixo++);
+ if (m->post_indent != -1 && m->post_indent > indent) {
+ /*
+ * The following line is indented more. So it is likely
+ * that this line is the start of a block.
+ */
+ s->penalty += any_blanks ?
+ RELATIVE_OUTDENT_WITH_BLANK_PENALTY :
+ RELATIVE_OUTDENT_PENALTY;
+ } else {
+ /*
+ * That was probably the end of a block.
+ */
+ s->penalty += any_blanks ?
+ RELATIVE_DEDENT_WITH_BLANK_PENALTY :
+ RELATIVE_DEDENT_PENALTY;
+ }
+ }
+}
+
+static int score_cmp(struct split_score *s1, struct split_score *s2)
+{
+ /* -1 if s1.effective_indent < s2->effective_indent, etc. */
+ int cmp_indents = ((s1->effective_indent > s2->effective_indent) -
+ (s1->effective_indent < s2->effective_indent));
+
+ return INDENT_WEIGHT * cmp_indents + (s1->penalty - s2->penalty);
+}
+
+/*
+ * Represent a group of changed lines in an xdfile_t (i.e., a contiguous group
+ * of lines that was inserted or deleted from the corresponding version of the
+ * file). We consider there to be such a group at the beginning of the file, at
+ * the end of the file, and between any two unchanged lines, though most such
+ * groups will usually be empty.
+ *
+ * If the first line in a group is equal to the line following the group, then
+ * the group can be slid down. Similarly, if the last line in a group is equal
+ * to the line preceding the group, then the group can be slid up. See
+ * group_slide_down() and group_slide_up().
+ *
+ * Note that loops that are testing for changed lines in xdf->rchg do not need
+ * index bounding since the array is prepared with a zero at position -1 and N.
+ */
+struct group {
+ /*
+ * The index of the first changed line in the group, or the index of
+ * the unchanged line above which the (empty) group is located.
+ */
+ long start;
+
+ /*
+ * The index of the first unchanged line after the group. For an empty
+ * group, end is equal to start.
+ */
+ long end;
+};
+
+/*
+ * Initialize g to point at the first group in xdf.
+ */
+static void group_init(xdfile_t *xdf, struct group *g)
+{
+ g->start = g->end = 0;
+ while (xdf->rchg[g->end])
+ g->end++;
+}
+
+/*
+ * Move g to describe the next (possibly empty) group in xdf and return 0. If g
+ * is already at the end of the file, do nothing and return -1.
+ */
+static inline int group_next(xdfile_t *xdf, struct group *g)
+{
+ if (g->end == xdf->nrec)
+ return -1;
+ g->start = g->end + 1;
+ for (g->end = g->start; xdf->rchg[g->end]; g->end++)
+ ;
+
+ return 0;
+}
+
+/*
+ * Move g to describe the previous (possibly empty) group in xdf and return 0.
+ * If g is already at the beginning of the file, do nothing and return -1.
+ */
+static inline int group_previous(xdfile_t *xdf, struct group *g)
+{
+ if (g->start == 0)
+ return -1;
+
+ g->end = g->start - 1;
+ for (g->start = g->end; xdf->rchg[g->start - 1]; g->start--)
+ ;
+
+ return 0;
+}
+
+/*
+ * If g can be slid toward the end of the file, do so, and if it bumps into a
+ * following group, expand this group to include it. Return 0 on success or -1
+ * if g cannot be slid down.
+ */
+static int group_slide_down(xdfile_t *xdf, struct group *g, long flags)
+{
+ if (g->end < xdf->nrec &&
+ recs_match(xdf->recs[g->start], xdf->recs[g->end], flags)) {
+ xdf->rchg[g->start++] = 0;
+ xdf->rchg[g->end++] = 1;
+
+ while (xdf->rchg[g->end])
+ g->end++;
+
+ return 0;
+ } else {
+ return -1;
+ }
+}
+
+/*
+ * If g can be slid toward the beginning of the file, do so, and if it bumps
+ * into a previous group, expand this group to include it. Return 0 on success
+ * or -1 if g cannot be slid up.
+ */
+static int group_slide_up(xdfile_t *xdf, struct group *g, long flags)
+{
+ if (g->start > 0 &&
+ recs_match(xdf->recs[g->start - 1], xdf->recs[g->end - 1], flags)) {
+ xdf->rchg[--g->start] = 1;
+ xdf->rchg[--g->end] = 0;
+
+ while (xdf->rchg[g->start - 1])
+ g->start--;
+
+ return 0;
+ } else {
+ return -1;
+ }
+}
+
+static void xdl_bug(const char *msg)
+{
+ fprintf(stderr, "BUG: %s\n", msg);
+ exit(1);
+}
+
+/*
+ * Move back and forward change groups for a consistent and pretty diff output.
+ * This also helps in finding joinable change groups and reducing the diff
+ * size.
+ */
+int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
+ struct group g, go;
+ long earliest_end, end_matching_other;
+ long groupsize;
+ unsigned int blank_lines;
+
+ group_init(xdf, &g);
+ group_init(xdfo, &go);
+
+ while (1) {
+ /* If the group is empty in the to-be-compacted file, skip it: */
+ if (g.end == g.start)
+ goto next;
+
+ /*
+ * Now shift the change up and then down as far as possible in
+ * each direction. If it bumps into any other changes, merge them.
+ */
do {
- grpsiz = ix - ixs;
- blank_lines = 0;
+ groupsize = g.end - g.start;
/*
- * If the line before the current change group, is equal to
- * the last line of the current change group, shift backward
- * the group.
+ * Keep track of the last "end" index that causes this
+ * group to align with a group of changed lines in the
+ * other file. -1 indicates that we haven't found such
+ * a match yet:
*/
- while (ixs > 0 && recs_match(recs, ixs - 1, ix - 1, flags)) {
- rchg[--ixs] = 1;
- rchg[--ix] = 0;
-
- /*
- * This change might have joined two change groups,
- * so we try to take this scenario in account by moving
- * the start index accordingly (and so the other-file
- * end-of-group index).
- */
- for (; rchg[ixs - 1]; ixs--);
- while (rchgo[--ixo]);
- }
+ end_matching_other = -1;
/*
- * Record the end-of-group position in case we are matched
- * with a group of changes in the other file (that is, the
- * change record before the end-of-group index in the other
- * file is set).
+ * Boolean value that records whether there are any blank
+ * lines that could be made to be the last line of this
+ * group.
*/
- ixref = rchgo[ixo - 1] ? ix: nrec;
+ blank_lines = 0;
+
+ /* Shift the group backward as much as possible: */
+ while (!group_slide_up(xdf, &g, flags))
+ if (group_previous(xdfo, &go))
+ xdl_bug("group sync broken sliding up");
/*
- * If the first line of the current change group, is equal to
- * the line next of the current change group, shift forward
- * the group.
+ * This is this highest that this group can be shifted.
+ * Record its end index:
*/
- while (ix < nrec && recs_match(recs, ixs, ix, flags)) {
- blank_lines += is_blank_line(recs, ix, flags);
-
- rchg[ixs++] = 0;
- rchg[ix++] = 1;
-
- /*
- * This change might have joined two change groups,
- * so we try to take this scenario in account by moving
- * the start index accordingly (and so the other-file
- * end-of-group index). Keep tracking the reference
- * index in case we are shifting together with a
- * corresponding group of changes in the other file.
- */
- for (; rchg[ix]; ix++);
- while (rchgo[++ixo])
- ixref = ix;
- }
- } while (grpsiz != ix - ixs);
+ earliest_end = g.end;
- /*
- * Try to move back the possibly merged group of changes, to match
- * the recorded position in the other file.
- */
- while (ixref < ix) {
- rchg[--ixs] = 1;
- rchg[--ix] = 0;
- while (rchgo[--ixo]);
- }
+ if (go.end > go.start)
+ end_matching_other = g.end;
+
+ /* Now shift the group forward as far as possible: */
+ while (1) {
+ if (!blank_lines)
+ blank_lines = is_blank_line(
+ xdf->recs[g.end - 1],
+ flags);
+
+ if (group_slide_down(xdf, &g, flags))
+ break;
+ if (group_next(xdfo, &go))
+ xdl_bug("group sync broken sliding down");
+
+ if (go.end > go.start)
+ end_matching_other = g.end;
+ }
+ } while (groupsize != g.end - g.start);
/*
- * If a group can be moved back and forth, see if there is a
- * blank line in the moving space. If there is a blank line,
- * make sure the last blank line is the end of the group.
+ * If the group can be shifted, then we can possibly use this
+ * freedom to produce a more intuitive diff.
*
- * As we already shifted the group forward as far as possible
- * in the earlier loop, we need to shift it back only if at all.
+ * The group is currently shifted as far down as possible, so the
+ * heuristics below only have to handle upwards shifts.
*/
- if ((flags & XDF_COMPACTION_HEURISTIC) && blank_lines) {
- while (ixs > 0 &&
- !is_blank_line(recs, ix - 1, flags) &&
- recs_match(recs, ixs - 1, ix - 1, flags)) {
- rchg[--ixs] = 1;
- rchg[--ix] = 0;
+
+ if (g.end == earliest_end) {
+ /* no shifting was possible */
+ } else if (end_matching_other != -1) {
+ /*
+ * Move the possibly merged group of changes back to line
+ * up with the last group of changes from the other file
+ * that it can align with.
+ */
+ while (go.end == go.start) {
+ if (group_slide_up(xdf, &g, flags))
+ xdl_bug("match disappeared");
+ if (group_previous(xdfo, &go))
+ xdl_bug("group sync broken sliding to match");
+ }
+ } else if ((flags & XDF_COMPACTION_HEURISTIC) && blank_lines) {
+ /*
+ * Compaction heuristic: if it is possible to shift the
+ * group to make its bottom line a blank line, do so.
+ *
+ * As we already shifted the group forward as far as
+ * possible in the earlier loop, we only need to handle
+ * backward shifts, not forward ones.
+ */
+ while (!is_blank_line(xdf->recs[g.end - 1], flags)) {
+ if (group_slide_up(xdf, &g, flags))
+ xdl_bug("blank line disappeared");
+ if (group_previous(xdfo, &go))
+ xdl_bug("group sync broken sliding to blank line");
+ }
+ } else if (flags & XDF_INDENT_HEURISTIC) {
+ /*
+ * Indent heuristic: a group of pure add/delete lines
+ * implies two splits, one between the end of the "before"
+ * context and the start of the group, and another between
+ * the end of the group and the beginning of the "after"
+ * context. Some splits are aesthetically better and some
+ * are worse. We compute a badness "score" for each split,
+ * and add the scores for the two splits to define a
+ * "score" for each position that the group can be shifted
+ * to. Then we pick the shift with the lowest score.
+ */
+ long shift, best_shift = -1;
+ struct split_score best_score;
+
+ for (shift = earliest_end; shift <= g.end; shift++) {
+ struct split_measurement m;
+ struct split_score score = {0, 0};
+
+ measure_split(xdf, shift, &m);
+ score_add_split(&m, &score);
+ measure_split(xdf, shift - groupsize, &m);
+ score_add_split(&m, &score);
+ if (best_shift == -1 ||
+ score_cmp(&score, &best_score) <= 0) {
+ best_score.effective_indent = score.effective_indent;
+ best_score.penalty = score.penalty;
+ best_shift = shift;
+ }
+ }
+
+ while (g.end > best_shift) {
+ if (group_slide_up(xdf, &g, flags))
+ xdl_bug("best shift unreached");
+ if (group_previous(xdfo, &go))
+ xdl_bug("group sync broken sliding to blank line");
}
}
+
+ next:
+ /* Move past the just-processed group: */
+ if (group_next(xdf, &g))
+ break;
+ if (group_next(xdfo, &go))
+ xdl_bug("group sync broken moving to next group");
}
+ if (!group_next(xdfo, &go))
+ xdl_bug("group sync broken at end of file");
+
return 0;
}