blame: add config options to handle output for ignored lines

When ignoring commits, the commit that is blamed might not be
responsible for the change.  Users might want to know when a particular
line has a potentially inaccurate blame.  Furthermore, they might never
want to see the object hash of an ignored commit.

This patch adds two config options to control the output behavior.

The first option can identify ignored lines by specifying
blame.markIgnoredFiles.  When this option is set, each blame line is
marked with an '*'.

For example:
	278b6158d6fdb (Barret Rhoden  2016-04-11 13:57:54 -0400 26)
appears as:
	*278b6158d6fd (Barret Rhoden  2016-04-11 13:57:54 -0400 26)

where the '*' is placed before the commit, and the hash has one fewer
characters.

Sometimes we are unable to even guess at what commit touched a line.
These lines are 'unblamable.'  The second option,
blame.maskIgnoredUnblamables, will zero the hash of any unblamable line.

For example, say we ignore e5e8d36d04cbe:
	e5e8d36d04cbe (Barret Rhoden  2016-04-11 13:57:54 -0400 26)
appears as:
	0000000000000 (Barret Rhoden  2016-04-11 13:57:54 -0400 26)

Signed-off-by: Barret Rhoden <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Barret Rhoden

Documentation/blame-options.txt

@@ -115,7 +115,11 @@ take effect.
 	change never happened.  Lines that were changed or added by an ignored
 	commit will be blamed on the previous commit that changed that line or
 	nearby lines.  This option may be specified multiple times to ignore
-	more than one revision.
+	more than one revision.  If the `blame.markIgnoredLines` config option
+	is set, then lines that were changed by an ignored commit will be
+	marked with a `*` in the blame output.  If the
+	`blame.maskIgnoredUnblamables` config option is set, then those lines that
+	we could not attribute to another revision are outputted as all zeros.
 
 --ignore-revs-file <file>::
 	Ignore revisions listed in `file`, one unabbreviated object name per line.

Documentation/config/blame.txt

@@ -26,3 +26,12 @@ blame.ignoreRevsFile::
 	`#` are ignored.  This option may be repeated multiple times.  Empty
 	file names will reset the list of ignored revisions.  This option will
 	be handled before the command line option `--ignore-revs-file`.
+
+blame.maskIgnoredUnblamables::
+	Output an object hash of all zeros for lines that were changed by an ignored
+	revision and that we could not attribute to another revision in the output
+	of linkgit:git-blame[1].
+
+blame.markIgnoredLines::
+	Mark lines that were changed by an ignored revision with a '*' in the
+	output of linkgit:git-blame[1].

blame.c

@@ -480,6 +480,7 @@ void blame_coalesce(struct blame_scoreboard *sb)
 	for (ent = sb->ent; ent && (next = ent->next); ent = next) {
 		if (ent->suspect == next->suspect &&
 		    ent->s_lno + ent->num_lines == next->s_lno &&
+		    ent->ignored == next->ignored &&
 		    ent->unblamable == next->unblamable) {
 			ent->num_lines += next->num_lines;
 			ent->next = next->next;
@@ -732,6 +733,7 @@ static void split_overlap(struct blame_entry *split,
 	int chunk_end_lno;
 	memset(split, 0, sizeof(struct blame_entry [3]));
 
+	split[0].ignored = split[1].ignored = split[2].ignored = e->ignored;
 	split[0].unblamable = e->unblamable;
 	split[1].unblamable = e->unblamable;
 	split[2].unblamable = e->unblamable;
@@ -856,6 +858,7 @@ static struct blame_entry *split_blame_at(struct blame_entry *e, int len,
 	struct blame_entry *n = xcalloc(1, sizeof(struct blame_entry));
 
 	n->suspect = new_suspect;
+	n->ignored = e->ignored;
 	n->unblamable = e->unblamable;
 	n->lno = e->lno + len;
 	n->s_lno = e->s_lno + len;
@@ -921,6 +924,7 @@ static void ignore_blame_entry(struct blame_entry *e,
 	struct blame_line_tracker *line_blames;
 	int entry_len, nr_lines, i;
 
+	e->ignored = 1;
 	line_blames = xcalloc(sizeof(struct blame_line_tracker),
 			      e->num_lines);
 	guess_line_blames(e, parent, target, offset, parent_slno, parent_len,

blame.h

@@ -92,6 +92,7 @@ struct blame_entry {
 	 * scanning the lines over and over.
 	 */
 	unsigned score;
+	int ignored;
 	int unblamable;
 };
 

builtin/blame.c

@@ -53,6 +53,8 @@ static int show_progress;
 static char repeated_meta_color[COLOR_MAXLEN];
 static int coloring_mode;
 static struct string_list ignore_revs_file_list = STRING_LIST_INIT_NODUP;
+static int mask_ignored_unblamables;
+static int mark_ignored_lines;
 
 static struct date_mode blame_date_mode = { DATE_ISO8601 };
 static size_t blame_date_width;
@@ -347,7 +349,7 @@ static void emit_porcelain(struct blame_scoreboard *sb, struct blame_entry *ent,
 	char hex[GIT_MAX_HEXSZ + 1];
 
 	oid_to_hex_r(hex, &suspect->commit->object.oid);
-	if (ent->unblamable)
+	if (mask_ignored_unblamables && ent->unblamable)
 		memset(hex, '0', strlen(hex));
 	printf("%s %d %d %d\n",
 	       hex,
@@ -482,7 +484,11 @@ static void emit_other(struct blame_scoreboard *sb, struct blame_entry *ent, int
 			}
 		}
 
-		if (ent->unblamable)
+		if (mark_ignored_lines && ent->ignored) {
+			length--;
+			putchar('*');
+		}
+		if (mask_ignored_unblamables && ent->unblamable)
 			memset(hex, '0', length);
 		printf("%.*s", length, hex);
 		if (opt & OUTPUT_ANNOTATE_COMPAT) {
@@ -710,6 +716,14 @@ static int git_blame_config(const char *var, const char *value, void *cb)
 		string_list_insert(&ignore_revs_file_list, str);
 		return 0;
 	}
+	if (!strcmp(var, "blame.maskignoredunblamables")) {
+		mask_ignored_unblamables = git_config_bool(var, value);
+		return 0;
+	}
+	if (!strcmp(var, "blame.markignoredlines")) {
+		mark_ignored_lines = git_config_bool(var, value);
+		return 0;
+	}
 	if (!strcmp(var, "color.blame.repeatedlines")) {
 		if (color_parse_mem(value, strlen(value), repeated_meta_color))
 			warning(_("invalid color '%s' in color.blame.repeatedLines"),

t/t8013-blame-ignore-revs.sh

@@ -53,6 +53,7 @@ test_expect_success ignore_rev_changing_lines '
 # to have nothing in common with "line-one" or "line-two", to keep any
 # heuristics from matching them with any lines in the parent.
 test_expect_success ignore_rev_adding_unblamable_lines '
+	git config --add blame.maskIgnoredUnblamables true &&
 	test_write_lines line-one-change line-two-changed y3 y4 >file &&
 	git add file &&
 	test_tick &&
@@ -123,6 +124,39 @@ test_expect_success bad_files_and_revs '
 	test_i18ngrep "Invalid object name: NOREV" err
 	'
 
+# Commit Z will touch the first two lines.  Y touched all four.
+# 	A--B--X--Y--Z
+# The blame output when ignoring Z should be:
+# ^Y ... 1)
+# ^Y ... 2)
+# Y  ... 3)
+# Y  ... 4)
+# We're checking only the first character
+test_expect_success mark_ignored_lines '
+	git config --add blame.markIgnoredLines true &&
+
+	test_write_lines line-one-Z line-two-Z y3 y4 >file &&
+	git add file &&
+	test_tick &&
+	git commit -m Z &&
+	git tag Z &&
+
+	git blame --ignore-rev Z file >blame_raw &&
+	echo "*" >expect &&
+
+	sed -n "1p" blame_raw | cut -c1 >actual &&
+	test_cmp expect actual &&
+
+	sed -n "2p" blame_raw | cut -c1 >actual &&
+	test_cmp expect actual &&
+
+	sed -n "3p" blame_raw | cut -c1 >actual &&
+	! test_cmp expect actual &&
+
+	sed -n "4p" blame_raw | cut -c1 >actual &&
+	! test_cmp expect actual
+	'
+
 # Resetting the repo and creating:
 #
 # A--B--M