#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;
diff_detect_rename_default = git_config_rename(var, value);
return 0;
}
+ if (!strcmp(var, "diff.indentheuristic")) {
+ diff_indent_heuristic = git_config_bool(var, value);
+ if (diff_indent_heuristic)
+ diff_compaction_heuristic = 0;
+ return 0;
+ }
if (!strcmp(var, "diff.compactionheuristic")) {
diff_compaction_heuristic = git_config_bool(var, value);
+ if (diff_compaction_heuristic)
+ diff_indent_heuristic = 0;
return 0;
}
if (!strcmp(var, "diff.autorefreshindex")) {
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;
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);
--- /dev/null
+#!/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
+}
+
+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_done
flags));
}
+/*
+ * 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 {
+ /*
+ * Is the split at the end of the file (aside from any blank lines)?
+ */
+ 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 {
+ /*
+ * 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:
+ */
+ 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
}
} while (groupsize != g.end - g.start);
+ /*
+ * If the group can be shifted, then we can possibly use this
+ * freedom to produce a more intuitive diff.
+ *
+ * The group is currently shifted as far down as possible, so the
+ * heuristics below only have to handle upwards shifts.
+ */
+
if (g.end == earliest_end) {
/* no shifting was possible */
} else if (end_matching_other != -1) {
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: