[RFC/PATCH] builtin/blame: darken redundant line information

[Stefan Beller <sbeller@google.com>]

When using git-blame lots of lines contain redundant information, for
example in hunks that consist of multiple lines, the metadata (commit name,
author, timezone) are repeated. A reader may not be interested in those,
so darken them. The darkening is not just based on hunk, but actually
takes the previous lines content for that field to compare to.

Signed-off-by: Stefan Beller <sbeller@google.com>
---

 Example output (blame of blame): http://i.imgur.com/0Y12p2f.png

 builtin/blame.c | 135 ++++++++++++++++++++++++++++++++++++++++++++++----------
 color.h         |   1 +
 2 files changed, 112 insertions(+), 24 deletions(-)

diff --git a/builtin/blame.c b/builtin/blame.c
index d7a2df3b47..7f921df0e7 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -6,6 +6,7 @@
  */
 
 #include "cache.h"
+#include "color.h"
 #include "builtin.h"
 #include "commit.h"
 #include "diff.h"
@@ -282,7 +283,8 @@ static void found_guilty_entry(struct blame_entry *ent, void *data)
 }
 
 static const char *format_time(timestamp_t time, const char *tz_str,
-			       int show_raw_time)
+			       int show_raw_time,
+			       timestamp_t difftime, const char *difftz_str)
 {
 	static struct strbuf time_buf = STRBUF_INIT;
 
@@ -291,12 +293,41 @@ static const char *format_time(timestamp_t time, const char *tz_str,
 		strbuf_addf(&time_buf, "%"PRItime" %s", time, tz_str);
 	}
 	else {
-		const char *time_str;
+		const char *time_str, *prev_str;
 		size_t time_width;
 		int tz;
+
+		if (difftime)
+			prev_str = xstrdup(show_date(difftime,
+						     atoi(difftz_str),
+						     &blame_date_mode));
 		tz = atoi(tz_str);
 		time_str = show_date(time, tz, &blame_date_mode);
-		strbuf_addstr(&time_buf, time_str);
+
+
+		if (difftime) {
+			int len = strlen(prev_str) > strlen(time_str) ?
+				  strlen(time_str) : strlen(prev_str);
+			int i, j;
+			int last_nondigit = 0;
+			for (i = 0; i < len; i++) {
+				if (isdigit(time_str[i]) &&
+				    time_str[i] != prev_str[i])
+					break;
+				if (!isdigit(time_str[i])) {
+					strbuf_addstr(&time_buf, GIT_COLOR_DARK);
+					for (j = last_nondigit; j < i; j++)
+						strbuf_addch(&time_buf, time_str[j]);
+					strbuf_addstr(&time_buf, GIT_COLOR_RESET);
+					last_nondigit = i;
+				}
+			}
+			for (i = last_nondigit; i < strlen(time_str); i++)
+				strbuf_addch(&time_buf, time_str[i]);
+		} else {
+			strbuf_addstr(&time_buf, time_str);
+		}
+
 		/*
 		 * Add space paddings to time_buf to display a fixed width
 		 * string, and use time_width for display width calibration.
@@ -319,6 +350,7 @@ static const char *format_time(timestamp_t time, const char *tz_str,
 #define OUTPUT_NO_AUTHOR       0200
 #define OUTPUT_SHOW_EMAIL	0400
 #define OUTPUT_LINE_PORCELAIN 01000
+#define OUTPUT_SHOW_REDUNDANT 02000
 
 static void emit_porcelain_details(struct blame_origin *suspect, int repeat)
 {
@@ -366,19 +398,43 @@ static void emit_porcelain(struct blame_scoreboard *sb, struct blame_entry *ent,
 		putchar('\n');
 }
 
-static void emit_other(struct blame_scoreboard *sb, struct blame_entry *ent, int opt)
+static void emit_other(struct blame_scoreboard *sb,
+		       struct blame_entry *ent,
+		       struct blame_entry *prev,
+		       int opt)
 {
 	int cnt;
 	const char *cp;
 	struct blame_origin *suspect = ent->suspect;
-	struct commit_info ci;
+	struct commit_info ci, prev_ci;
 	char hex[GIT_MAX_HEXSZ + 1];
 	int show_raw_time = !!(opt & OUTPUT_RAW_TIMESTAMP);
+	int prev_same_field = 0;
+	const char *use_color, *reset_color = GIT_COLOR_RESET;
 
 	get_commit_info(suspect->commit, &ci, 1);
 	oid_to_hex_r(hex, &suspect->commit->object.oid);
 
 	cp = blame_nth_line(sb, ent->lno);
+
+	commit_info_init(&prev_ci);
+	if ((opt & OUTPUT_SHOW_REDUNDANT) && prev) {
+		get_commit_info(prev->suspect->commit, &prev_ci, 1);
+		if ((opt & OUTPUT_SHOW_SCORE) && ent->score == prev->score)
+			prev_same_field |= OUTPUT_SHOW_SCORE;
+		if ((opt & OUTPUT_SHOW_NAME) && prev->suspect && !strcmp(suspect->path, prev->suspect->path))
+			prev_same_field |= OUTPUT_SHOW_NAME;
+		if ((opt & OUTPUT_SHOW_NUMBER) &&
+		    ent->s_lno == prev->s_lno + prev->num_lines - 1)
+			prev_same_field |= OUTPUT_SHOW_NUMBER;
+		if (!(opt & OUTPUT_NO_AUTHOR)) {
+			if (((opt & OUTPUT_SHOW_EMAIL) &&
+			     !strcmp(ci.author_mail.buf, prev_ci.author_mail.buf)) ||
+			    !strcmp(ci.author.buf, prev_ci.author.buf))
+				prev_same_field |= OUTPUT_NO_AUTHOR;
+		}
+	}
+
 	for (cnt = 0; cnt < ent->num_lines; cnt++) {
 		char ch;
 		int length = (opt & OUTPUT_LONG_OBJECT_NAME) ? GIT_SHA1_HEXSZ : abbrev;
@@ -391,8 +447,12 @@ static void emit_other(struct blame_scoreboard *sb, struct blame_entry *ent, int
 				putchar('^');
 			}
 		}
+		use_color = GIT_COLOR_NORMAL;
+		if ((opt & OUTPUT_SHOW_REDUNDANT) && cnt > 0)
+			use_color = GIT_COLOR_DARK;
+
+		printf("%s%.*s%s", use_color, length, hex, reset_color);
 
-		printf("%.*s", length, hex);
 		if (opt & OUTPUT_ANNOTATE_COMPAT) {
 			const char *name;
 			if (opt & OUTPUT_SHOW_EMAIL)
@@ -401,20 +461,36 @@ static void emit_other(struct blame_scoreboard *sb, struct blame_entry *ent, int
 				name = ci.author.buf;
 			printf("\t(%10s\t%10s\t%d)", name,
 			       format_time(ci.author_time, ci.author_tz.buf,
-					   show_raw_time),
+					   show_raw_time, 0, NULL),
 			       ent->lno + 1 + cnt);
 		} else {
-			if (opt & OUTPUT_SHOW_SCORE)
-				printf(" %*d %02d",
+			if (opt & OUTPUT_SHOW_SCORE) {
+				use_color = GIT_COLOR_NORMAL;
+				if ((opt & OUTPUT_SHOW_REDUNDANT) &&
+				    (cnt > 0 || prev_same_field & OUTPUT_SHOW_SCORE))
+					use_color = GIT_COLOR_DARK;
+				printf(" %s%*d %02d%s", use_color,
 				       max_score_digits, ent->score,
-				       ent->suspect->refcnt);
-			if (opt & OUTPUT_SHOW_NAME)
-				printf(" %-*.*s", longest_file, longest_file,
-				       suspect->path);
-			if (opt & OUTPUT_SHOW_NUMBER)
-				printf(" %*d", max_orig_digits,
-				       ent->s_lno + 1 + cnt);
-
+				       ent->suspect->refcnt, reset_color);
+			}
+			if (opt & OUTPUT_SHOW_NAME) {
+				use_color = GIT_COLOR_NORMAL;
+				if ((opt & OUTPUT_SHOW_REDUNDANT) &&
+				    (cnt > 0 || prev_same_field & OUTPUT_SHOW_NAME))
+					use_color = GIT_COLOR_DARK;
+				printf(" %s%-*.*s%s", use_color, longest_file,
+						      longest_file,
+						      suspect->path,
+						      reset_color);
+			}
+			if (opt & OUTPUT_SHOW_NUMBER) {
+				use_color = GIT_COLOR_NORMAL;
+				if ((opt & OUTPUT_SHOW_REDUNDANT) &&
+				    (cnt > 0 || prev_same_field & OUTPUT_SHOW_NUMBER))
+					use_color = GIT_COLOR_DARK;
+				printf(" %s%*d%s", use_color, max_orig_digits,
+				       ent->s_lno + 1 + cnt, reset_color);
+			}
 			if (!(opt & OUTPUT_NO_AUTHOR)) {
 				const char *name;
 				int pad;
@@ -422,12 +498,21 @@ static void emit_other(struct blame_scoreboard *sb, struct blame_entry *ent, int
 					name = ci.author_mail.buf;
 				else
 					name = ci.author.buf;
+
+				use_color = GIT_COLOR_NORMAL;
+				if ((opt & OUTPUT_SHOW_REDUNDANT) &&
+				    (cnt > 0 || prev_same_field & OUTPUT_NO_AUTHOR))
+					use_color = GIT_COLOR_DARK;
+
 				pad = longest_author - utf8_strwidth(name);
-				printf(" (%s%*s %10s",
-				       name, pad, "",
-				       format_time(ci.author_time,
-						   ci.author_tz.buf,
-						   show_raw_time));
+				printf(" %s(%s%*s%s", use_color,
+						      name, pad, "",
+						      reset_color);
+				printf(" %10s", format_time(ci.author_time,
+							    ci.author_tz.buf,
+							    show_raw_time,
+							    prev_ci.author_time,
+							    prev_ci.author_tz.buf));
 			}
 			printf(" %*d) ",
 			       max_digits, ent->lno + 1 + cnt);
@@ -447,7 +532,7 @@ static void emit_other(struct blame_scoreboard *sb, struct blame_entry *ent, int
 
 static void output(struct blame_scoreboard *sb, int option)
 {
-	struct blame_entry *ent;
+	struct blame_entry *ent, *prev = NULL;
 
 	if (option & OUTPUT_PORCELAIN) {
 		for (ent = sb->ent; ent; ent = ent->next) {
@@ -469,7 +554,8 @@ static void output(struct blame_scoreboard *sb, int option)
 		if (option & OUTPUT_PORCELAIN)
 			emit_porcelain(sb, ent, option);
 		else {
-			emit_other(sb, ent, option);
+			emit_other(sb, ent, prev, option);
+			prev = ent;
 		}
 	}
 }
@@ -680,6 +766,7 @@ 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),
+		OPT_BIT('r', "redundant", &output_option, N_("darken redundancy from previous line (Default: off)"), OUTPUT_SHOW_REDUNDANT),
 
 		/*
 		 * The following two options are parsed by parse_revision_opt()
diff --git a/color.h b/color.h
index 90627650fc..bad2d7e29c 100644
--- a/color.h
+++ b/color.h
@@ -30,6 +30,7 @@ struct strbuf;
 #define GIT_COLOR_BLUE		"\033[34m"
 #define GIT_COLOR_MAGENTA	"\033[35m"
 #define GIT_COLOR_CYAN		"\033[36m"
+#define GIT_COLOR_DARK		"\033[1;30m"
 #define GIT_COLOR_BOLD_RED	"\033[1;31m"
 #define GIT_COLOR_BOLD_GREEN	"\033[1;32m"
 #define GIT_COLOR_BOLD_YELLOW	"\033[1;33m"
-- 
2.13.0.17.gf3d7728391