Merge branch 'by/line-log' into next

* by/line-log:
  Document line history browser
  Add tests for line history browser
  Add --full-line-diff option
  Add --graph prefix before line history output
  Add parent rewriting to line history browser
  Make graph_next_line external to other part of git
  Make rewrite_parents public to other part of git
  Hook line history into cmd_log, ensuring a topo-ordered walk
  Print the line log
  map/take range to the parent of commits
  Add range clone functions
  Export three functions from diff.c
  Parse the -L options
  Refactor parse_loc
  Add the basic data structure for line level history
  parse-options: add two helper functions
  parse-options: enhance STOP_AT_NON_OPTION

Conflicts:
	builtin/log.c

Documentation/blame-options.txt

@@ -13,24 +13,7 @@
 	Annotate only the given line range.  <start> and <end> can take
 	one of these forms:
 
-	- number
-+
-If <start> or <end> is a number, it specifies an
-absolute line number (lines count from 1).
-+
-
-- /regex/
-+
-This form will use the first line matching the given
-POSIX regex.  If <end> is a regex, it will search
-starting at the line given by <start>.
-+
-
-- +offset or -offset
-+
-This is only valid for <end> and will specify a number
-of lines before or after the line given by <start>.
-+
+include::line-range-format.txt[]
 
 -l::
 	Show long rev (Default: off).

Documentation/git-log.txt

@@ -9,6 +9,7 @@ git-log - Show commit logs
 SYNOPSIS
 --------
 'git log' [<options>] [<since>..<until>] [[\--] <path>...]
+'git log' [<options>] -L n,m <path>
 
 DESCRIPTION
 -----------
@@ -19,6 +20,9 @@ command to control what is shown and how, and options applicable to
 the 'git diff-*' commands to control how the changes
 each commit introduces are shown.
 
+With '-L' option, the command will help to trace the history of user specified
+line ranges. It can trace multiple ranges coming from multiple files.
+
 
 OPTIONS
 -------
@@ -66,6 +70,17 @@ produced by --stat etc.
 	Note that only message is considered, if also a diff is shown
 	its size is not included.
 
+-L <start>,<end>::
+	The line range.  <start> and <end> can take one of these forms:
+
+include::line-range-format.txt[]
+You can also specify this option more than once before each path.
+
+
+--full-line-diff::
+	Always print the interesting range even if the current commit
+	does not change any line of the range.
+
 [\--] <path>...::
 	Show only commits that affect any of the specified paths. To
 	prevent confusion with options and branch names, paths may need

Documentation/line-range-format.txt

@@ -0,0 +1,18 @@
+- number
++
+If <start> or <end> is a number, it specifies an
+absolute line number (lines count from 1).
++
+
+- /regex/
++
+This form will use the first line matching the given
+POSIX regex.  If <end> is a regex, it will search
+starting at the line given by <start>.
++
+
+- +offset or -offset
++
+This is only valid for <end> and will specify a number
+of lines before or after the line given by <start>.
++

Makefile

@@ -518,6 +518,7 @@ LIB_H += grep.h
 LIB_H += hash.h
 LIB_H += help.h
 LIB_H += levenshtein.h
+LIB_H += line.h
 LIB_H += list-objects.h
 LIB_H += ll-merge.h
 LIB_H += log-tree.h
@@ -608,6 +609,7 @@ LIB_OBJS += help.o
 LIB_OBJS += hex.o
 LIB_OBJS += ident.o
 LIB_OBJS += levenshtein.o
+LIB_OBJS += line.o
 LIB_OBJS += list-objects.o
 LIB_OBJS += ll-merge.o
 LIB_OBJS += lockfile.o

builtin/blame.c

@@ -21,6 +21,7 @@
 #include "parse-options.h"
 #include "utf8.h"
 #include "userdiff.h"
+#include "line.h"
 
 static char blame_usage[] = "git blame [options] [rev-opts] [rev] [--] file";
 
@@ -541,11 +542,16 @@ static void dup_entry(struct blame_entry *dst, struct blame_entry *src)
 	dst->score = 0;
 }
 
-static const char *nth_line(struct scoreboard *sb, int lno)
+static const char *nth_line(struct scoreboard *sb, long lno)
 {
 	return sb->final_buf + sb->lineno[lno];
 }
 
+static const char *nth_line_cb(void *data, long lno)
+{
+	return nth_line((struct scoreboard *)data, lno);
+}
+
 /*
  * It is known that lines between tlno to same came from parent, and e
  * has an overlap with that range.  it also is known that parent's
@@ -1898,83 +1904,6 @@ static const char *add_prefix(const char *prefix, const char *path)
 	return prefix_path(prefix, prefix ? strlen(prefix) : 0, path);
 }
 
-/*
- * Parsing of (comma separated) one item in the -L option
- */
-static const char *parse_loc(const char *spec,
-			     struct scoreboard *sb, long lno,
-			     long begin, long *ret)
-{
-	char *term;
-	const char *line;
-	long num;
-	int reg_error;
-	regex_t regexp;
-	regmatch_t match[1];
-
-	/* Allow "-L <something>,+20" to mean starting at <something>
-	 * for 20 lines, or "-L <something>,-5" for 5 lines ending at
-	 * <something>.
-	 */
-	if (1 < begin && (spec[0] == '+' || spec[0] == '-')) {
-		num = strtol(spec + 1, &term, 10);
-		if (term != spec + 1) {
-			if (spec[0] == '-')
-				num = 0 - num;
-			if (0 < num)
-				*ret = begin + num - 2;
-			else if (!num)
-				*ret = begin;
-			else
-				*ret = begin + num;
-			return term;
-		}
-		return spec;
-	}
-	num = strtol(spec, &term, 10);
-	if (term != spec) {
-		*ret = num;
-		return term;
-	}
-	if (spec[0] != '/')
-		return spec;
-
-	/* it could be a regexp of form /.../ */
-	for (term = (char *) spec + 1; *term && *term != '/'; term++) {
-		if (*term == '\\')
-			term++;
-	}
-	if (*term != '/')
-		return spec;
-
-	/* try [spec+1 .. term-1] as regexp */
-	*term = 0;
-	begin--; /* input is in human terms */
-	line = nth_line(sb, begin);
-
-	if (!(reg_error = regcomp(&regexp, spec + 1, REG_NEWLINE)) &&
-	    !(reg_error = regexec(&regexp, line, 1, match, 0))) {
-		const char *cp = line + match[0].rm_so;
-		const char *nline;
-
-		while (begin++ < lno) {
-			nline = nth_line(sb, begin);
-			if (line <= cp && cp < nline)
-				break;
-			line = nline;
-		}
-		*ret = begin;
-		regfree(&regexp);
-		*term++ = '/';
-		return term;
-	}
-	else {
-		char errbuf[1024];
-		regerror(reg_error, &regexp, errbuf, 1024);
-		die("-L parameter '%s': %s", spec + 1, errbuf);
-	}
-}
-
 /*
  * Parsing of -L option
  */
@@ -1985,9 +1914,9 @@ static void prepare_blame_range(struct scoreboard *sb,
 {
 	const char *term;
 
-	term = parse_loc(bottomtop, sb, lno, 1, bottom);
+	term = parse_loc(bottomtop, nth_line_cb, sb, lno, 1, bottom);
 	if (*term == ',') {
-		term = parse_loc(term + 1, sb, lno, *bottom + 1, top);
+		term = parse_loc(term + 1, nth_line_cb, sb, lno, *bottom + 1, top);
 		if (*term)
 			usage(blame_usage);
 	}

builtin/log.c

@@ -19,6 +19,7 @@
 #include "remote.h"
 #include "string-list.h"
 #include "parse-options.h"
+#include "line.h"
 
 /* Set a default date-time format for git log ("log.date" config variable) */
 static const char *default_date_mode = NULL;
@@ -27,11 +28,24 @@ static int default_show_root = 1;
 static int decoration_style;
 static const char *fmt_patch_subject_prefix = "PATCH";
 static const char *fmt_pretty;
+static const char *dashdash = "--";
 
-static const char * const builtin_log_usage =
+static char builtin_log_usage[] =
 	"git log [<options>] [<since>..<until>] [[--] <path>...]\n"
+	"git log [<options>] -L n,m <path>\n"
 	"   or: git show [options] <object>...";
 
+static const char *log_opt_usage[] = {
+	builtin_log_usage,
+	NULL
+};
+
+struct line_opt_callback_data {
+	struct diff_line_range **range;
+	struct parse_opt_ctx_t *ctx;
+	struct rev_info *rev;
+};
+
 static int parse_decoration_style(const char *var, const char *value)
 {
 	switch (git_config_maybe_bool(var, value)) {
@@ -49,12 +63,48 @@ static int parse_decoration_style(const char *var, const char *value)
 	return -1;
 }
 
+static int log_line_range_callback(const struct option *option, const char *arg, int unset)
+{
+	struct line_opt_callback_data *data = option->value;
+	struct diff_line_range *r = *data->range;
+	struct parse_opt_ctx_t *ctx = data->ctx;
+
+	if (!arg)
+		return -1;
+
+	if (r->nr == 0 && r->next == NULL)
+		ctx->out[ctx->cpidx++] = dashdash;
+
+	diff_line_range_append(r, arg);
+	data->rev->line_level_traverse = 1;
+	return 0;
+}
+
 static void cmd_log_init(int argc, const char **argv, const char *prefix,
 			 struct rev_info *rev, struct setup_revision_opt *opt)
 {
 	int i;
 	int decoration_given = 0;
+	static int full_line_diff;
 	struct userformat_want w;
+	const char *path = NULL, *fullpath = NULL;
+	static struct diff_line_range *range;
+	struct diff_line_range *r = NULL;
+	static struct parse_opt_ctx_t ctx;
+	static struct line_opt_callback_data line_cb = {&range, &ctx, NULL};
+	static const struct option options[] = {
+		OPT_CALLBACK('L', NULL, &line_cb, "n,m",
+			     "Process only line range n,m, counting from 1",
+			     log_line_range_callback),
+		OPT_BOOLEAN(0, "full-line-diff", &full_line_diff,
+			    "Always print the interesting range even if the \
+			    current commit does not change any line of it"),
+		OPT_END()
+	};
+
+	line_cb.rev = rev;
+	range = xmalloc(sizeof(*range));
+	DIFF_LINE_RANGE_INIT(range);
 
 	rev->abbrev = DEFAULT_ABBREV;
 	rev->commit_format = CMIT_FMT_DEFAULT;
@@ -75,6 +125,56 @@ static void cmd_log_init(int argc, const char **argv, const char *prefix,
 	 */
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage(builtin_log_usage);
+
+	parse_options_start(&ctx, argc, argv, prefix, PARSE_OPT_KEEP_DASHDASH |
+			PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_STOP_AT_NON_OPTION);
+	for (;;) {
+		switch (parse_options_step(&ctx, options, log_opt_usage)) {
+		case PARSE_OPT_HELP:
+			exit(129);
+		case PARSE_OPT_DONE:
+			goto parse_done;
+		case PARSE_OPT_NON_OPTION:
+			path = parse_options_current(&ctx);
+			fullpath = prefix_path(prefix, prefix ? strlen(prefix) : 0, path);
+			range->spec = alloc_filespec(fullpath);
+			free((void *)fullpath);
+			if (range->nr == 0) {
+				if (range->next) {
+					die("Path %s need a -L <range> option\n"
+					"If you want follow the history of the whole file "
+					"use 'git log -L 1,$ <path>'", range->spec->path);
+				} else {
+					parse_options_next(&ctx, 1);
+					continue;
+				}
+			}
+			r = xmalloc(sizeof(*r));
+			DIFF_LINE_RANGE_INIT(r);
+			r->next = range;
+			range = r;
+			parse_options_next(&ctx, 1);
+			continue;
+		case PARSE_OPT_UNKNOWN:
+			parse_options_next(&ctx, 1);
+			continue;
+		}
+
+		parse_revision_opt(rev, &ctx, options, log_opt_usage);
+	}
+parse_done:
+	argc = parse_options_end(&ctx);
+
+	/* die if '-L <range>' with no pathspec follow */
+	if (range->nr > 0 && range->spec == NULL)
+		die("Each -L should follow a path");
+	/* clear up the last range */
+	if (range->nr == 0) {
+		struct diff_line_range *r = range->next;
+		DIFF_LINE_RANGE_CLEAR(range);
+		range = r;
+	}
+
 	argc = setup_revisions(argc, argv, rev, opt);
 
 	memset(&w, 0, sizeof(w));
@@ -125,6 +225,12 @@ static void cmd_log_init(int argc, const char **argv, const char *prefix,
 		rev->show_decorations = 1;
 		load_ref_decorations(decoration_style);
 	}
+
+	/* Test whether line level history is asked for */
+	if (range && range->nr > 0) {
+		setup_line(rev, range);
+		rev->full_line_diff = full_line_diff;
+	}
 	setup_pager();
 }
 
@@ -510,7 +616,10 @@ int cmd_log(int argc, const char **argv, const char *prefix)
 	memset(&opt, 0, sizeof(opt));
 	opt.def = "HEAD";
 	cmd_log_init(argc, argv, prefix, &rev, &opt);
-	return cmd_log_walk(&rev);
+	if (rev.line_level_traverse)
+		return cmd_line_log_walk(&rev);
+	else
+		return cmd_log_walk(&rev);
 }
 
 /* format-patch */

diff.c

@@ -151,7 +151,7 @@ int git_diff_basic_config(const char *var, const char *value, void *cb)
 	return git_color_default_config(var, value, cb);
 }
 
-static char *quote_two(const char *one, const char *two)
+char *quote_two(const char *one, const char *two)
 {
 	int need_one = quote_c_style(one, NULL, NULL, 1);
 	int need_two = quote_c_style(two, NULL, NULL, 1);
@@ -332,7 +332,7 @@ static void emit_line_0(struct diff_options *o, const char *set, const char *res
 		fputc('\n', file);
 }
 
-static void emit_line(struct diff_options *o, const char *set, const char *reset,
+void emit_line(struct diff_options *o, const char *set, const char *reset,
 		      const char *line, int len)
 {
 	emit_line_0(o, set, reset, line[0], line+1, len-1);
@@ -2571,7 +2571,7 @@ static int similarity_index(struct diff_filepair *p)
 	return p->score * 100 / MAX_SCORE;
 }
 
-static void fill_metainfo(struct strbuf *msg,
+void fill_metainfo(struct strbuf *msg,
 			  const char *name,
 			  const char *other,
 			  struct diff_filespec *one,

diff.h

@@ -12,6 +12,7 @@ struct diff_queue_struct;
 struct strbuf;
 struct diff_filespec;
 struct userdiff_driver;
+struct diff_filepair;
 
 typedef void (*change_fn_t)(struct diff_options *options,
 		 unsigned old_mode, unsigned new_mode,
@@ -312,4 +313,20 @@ extern size_t fill_textconv(struct userdiff_driver *driver,
 
 extern struct userdiff_driver *get_textconv(struct diff_filespec *one);
 
+/* some output functions line.c need */
+extern void fill_metainfo(struct strbuf *msg,
+			  const char *name,
+			  const char *other,
+			  struct diff_filespec *one,
+			  struct diff_filespec *two,
+			  struct diff_options *o,
+			  struct diff_filepair *p,
+			  int *must_show_header,
+			  int use_color);
+
+extern void emit_line(struct diff_options *o, const char *set, const char *reset,
+		      const char *line, int len);
+
+extern char *quote_two(const char *one, const char *two);
+
 #endif /* DIFF_H */

line.h

@@ -0,0 +1,141 @@
+#ifndef LINE_H
+#define LINE_H
+
+#include "diffcore.h"
+
+struct rev_info;
+struct commit;
+struct diff_line_range;
+struct diff_options;
+
+typedef const char *(*nth_line_fn_t)(void *data, long lno);
+
+struct print_range {
+	int start, end;		/* Line range of post-image */
+	int pstart, pend;	/* Line range of pre-image */
+	int line_added : 1;	/* whether this range is added */
+};
+
+struct print_pair {
+	int alloc, nr;
+	struct print_range *ranges;
+};
+
+#define PRINT_RANGE_INIT(r) \
+	do { \
+		(r)->start = (r)->end = 0; \
+		(r)->pstart = (r)->pend = 0; \
+		(r)->line_added = 0; \
+	} while (0)
+
+#define PRINT_PAIR_INIT(p) \
+	do { \
+		(p)->alloc = (p)->nr = 0; \
+		(p)->ranges = NULL; \
+	} while (0)
+
+#define PRINT_PAIR_GROW(p) \
+	do { \
+		(p)->nr++; \
+		ALLOC_GROW((p)->ranges, (p)->nr, (p)->alloc); \
+	} while (0)
+
+#define PRINT_PAIR_CLEAR(p) \
+	do { \
+		(p)->alloc = (p)->nr = 0; \
+		if ((p)->ranges) \
+			free((p)->ranges); \
+		(p)->ranges = NULL; \
+	} while (0)
+
+struct line_range {
+	const char *arg;	/* The argument to specify this line range */
+	long start, end;	/* The interesting line range of current commit */
+	long pstart, pend;	/* The corresponding range of parent commit */
+	struct print_pair pair;
+			/* The changed lines inside this range */
+	unsigned int diff:1;
+};
+
+struct diff_line_range {
+	struct diff_filespec *prev;
+	struct diff_filespec *spec;
+	char status;
+	int alloc;
+	int nr;
+	struct line_range *ranges;
+	unsigned int	touch:1,
+			diff:1;
+	struct diff_line_range *next;
+};
+
+#define RANGE_INIT(r) \
+	do { \
+		(r)->arg = NULL; \
+		(r)->start = (r)->end = 0; \
+		(r)->pstart = (r)->pend = 0; \
+		PRINT_PAIR_INIT(&((r)->pair)); \
+		(r)->diff = 0; \
+	} while (0)
+
+#define RANGE_CLEAR(r) \
+	do { \
+		(r)->arg = NULL; \
+		(r)->start = (r)->end = 0; \
+		(r)->pstart = (r)->pend = 0; \
+		PRINT_PAIR_CLEAR(&r->pair); \
+		(r)->diff = 0; \
+	} while (0)
+
+#define DIFF_LINE_RANGE_INIT(r) \
+	do { \
+		(r)->prev = (r)->spec = NULL; \
+		(r)->status = '\0'; \
+		(r)->alloc = (r)->nr = 0; \
+		(r)->ranges = NULL; \
+		(r)->next = NULL; \
+		(r)->touch = 0; \
+		(r)->diff = 0; \
+	} while (0)
+
+#define DIFF_LINE_RANGE_GROW(r) \
+	do { \
+		(r)->nr++; \
+		ALLOC_GROW((r)->ranges, (r)->nr, (r)->alloc); \
+		RANGE_INIT(((r)->ranges + (r)->nr - 1)); \
+	} while (0)
+
+#define DIFF_LINE_RANGE_CLEAR(r) \
+	diff_line_range_clear((r));
+
+extern struct line_range *diff_line_range_insert(struct diff_line_range *r,
+		const char *arg, int start, int end);
+
+extern void diff_line_range_append(struct diff_line_range *r, const char *arg);
+
+extern void diff_line_range_clear(struct diff_line_range *r);
+
+extern struct diff_line_range *diff_line_range_merge(
+		struct diff_line_range *out,
+		struct diff_line_range *other);
+
+extern struct diff_line_range *diff_line_range_clone(struct diff_line_range *r);
+
+extern struct diff_line_range *diff_line_range_clone_deeply(struct diff_line_range *r);
+
+extern void setup_line(struct rev_info *rev, struct diff_line_range *r);
+
+extern void add_line_range(struct rev_info *revs, struct commit *commit,
+		struct diff_line_range *r);
+
+extern struct diff_line_range *lookup_line_range(struct rev_info *revs,
+		struct commit *commit);
+
+const char *parse_loc(const char *spec, nth_line_fn_t nth_line,
+		void *data, long lines, long begin, long *ret);
+
+extern int cmd_line_log_walk(struct rev_info *rev);
+
+extern void limit_list_line(struct rev_info *rev);
+
+#endif

parse-options.c

@@ -374,7 +374,7 @@ int parse_options_step(struct parse_opt_ctx_t *ctx,
 			if (parse_nodash_opt(ctx, arg, options) == 0)
 				continue;
 			if (ctx->flags & PARSE_OPT_STOP_AT_NON_OPTION)
-				break;
+				return PARSE_OPT_NON_OPTION;
 			ctx->out[ctx->cpidx++] = ctx->argv[0];
 			continue;
 		}
@@ -439,6 +439,25 @@ unknown:
 	return PARSE_OPT_DONE;
 }
 
+const char *parse_options_current(struct parse_opt_ctx_t *ctx)
+{
+	return ctx->argv[0];
+}
+
+int parse_options_next(struct parse_opt_ctx_t *ctx, int keep)
+{
+	if (ctx->argc <= 0)
+		return -1;
+
+	if (keep)
+		ctx->out[ctx->cpidx++] = ctx->argv[0];
+
+	ctx->argc--;
+	ctx->argv++;
+
+	return 0;
+}
+
 int parse_options_end(struct parse_opt_ctx_t *ctx)
 {
 	memmove(ctx->out + ctx->cpidx, ctx->argv, ctx->argc * sizeof(*ctx->out));
@@ -456,6 +475,7 @@ int parse_options(int argc, const char **argv, const char *prefix,
 	switch (parse_options_step(&ctx, options, usagestr)) {
 	case PARSE_OPT_HELP:
 		exit(129);
+	case PARSE_OPT_NON_OPTION:
 	case PARSE_OPT_DONE:
 		break;
 	default: /* PARSE_OPT_UNKNOWN */

parse-options.h

@@ -161,7 +161,8 @@ extern NORETURN void usage_msg_opt(const char *msg,
 enum {
 	PARSE_OPT_HELP = -1,
 	PARSE_OPT_DONE,
-	PARSE_OPT_UNKNOWN
+	PARSE_OPT_NON_OPTION,
+	PARSE_OPT_UNKNOWN,
 };
 
 /*
@@ -186,6 +187,10 @@ extern int parse_options_step(struct parse_opt_ctx_t *ctx,
 			      const struct option *options,
 			      const char * const usagestr[]);
 
+extern const char *parse_options_current(struct parse_opt_ctx_t *ctx);
+
+extern int parse_options_next(struct parse_opt_ctx_t *ctx, int keep);
+
 extern int parse_options_end(struct parse_opt_ctx_t *ctx);
 
 extern int parse_options_concat(struct option *dst, size_t, struct option *src);

revision.c

@@ -13,6 +13,7 @@
 #include "decorate.h"
 #include "log-tree.h"
 #include "string-list.h"
+#include "line.h"
 
 volatile show_early_output_fn_t show_early_output;
 
@@ -1662,6 +1663,12 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	if (revs->combine_merges)
 		revs->ignore_merges = 0;
 	revs->diffopt.abbrev = revs->abbrev;
+
+	if (revs->line_level_traverse) {
+		revs->limited = 1;
+		revs->topo_order = 1;
+	}
+
 	if (diff_setup_done(&revs->diffopt) < 0)
 		die("diff_setup_done failed");
 
@@ -1905,6 +1912,11 @@ int prepare_revision_walk(struct rev_info *revs)
 			return -1;
 	if (revs->topo_order)
 		sort_in_topological_order(&revs->commits, revs->lifo);
+	if (revs->full_line_diff)
+		revs->dense = 0;
+	if (revs->rewrite_parents && revs->line_level_traverse
+		&& !revs->full_line_diff)
+		limit_list_line(revs);
 	if (revs->simplify_merges)
 		simplify_merges(revs);
 	if (revs->children.name)
@@ -1912,12 +1924,6 @@ int prepare_revision_walk(struct rev_info *revs)
 	return 0;
 }
 
-enum rewrite_result {
-	rewrite_one_ok,
-	rewrite_one_noparents,
-	rewrite_one_error
-};
-
 static enum rewrite_result rewrite_one(struct rev_info *revs, struct commit **pp)
 {
 	struct commit_list *cache = NULL;
@@ -1939,12 +1945,13 @@ static enum rewrite_result rewrite_one(struct rev_info *revs, struct commit **pp
 	}
 }
 
-static int rewrite_parents(struct rev_info *revs, struct commit *commit)
+int rewrite_parents(struct rev_info *revs, struct commit *commit,
+	rewrite_parent_fn_t rewrite_parent)
 {
 	struct commit_list **pp = &commit->parents;
 	while (*pp) {
 		struct commit_list *parent = *pp;
-		switch (rewrite_one(revs, &parent->item)) {
+		switch (rewrite_parent(revs, &parent->item)) {
 		case rewrite_one_ok:
 			break;
 		case rewrite_one_noparents:
@@ -2012,7 +2019,7 @@ enum commit_action simplify_commit(struct rev_info *revs, struct commit *commit)
 	if (action == commit_show &&
 	    !revs->show_all &&
 	    revs->prune && revs->dense && want_ancestry(revs)) {
-		if (rewrite_parents(revs, commit) < 0)
+		if (rewrite_parents(revs, commit, rewrite_one) < 0)
 			return commit_error;
 	}
 	return action;

revision.h

@@ -14,7 +14,11 @@
 #define CHILD_SHOWN	(1u<<6)
 #define ADDED		(1u<<7)	/* Parents already parsed and added? */
 #define SYMMETRIC_LEFT	(1u<<8)
-#define ALL_REV_FLAGS	((1u<<9)-1)
+#define RANGE_UPDATE	(1u<<9) /* for line level traverse */
+#define NEED_PRINT	(1u<<10)
+#define NONTRIVIAL_MERGE	(1u<<11)
+#define EVIL_MERGE	(1u<<12)
+#define ALL_REV_FLAGS	((1u<<13)-1)
 
 #define DECORATE_SHORT_REFS	1
 #define DECORATE_FULL_REFS	2
@@ -68,7 +72,9 @@ struct rev_info {
 			cherry_pick:1,
 			bisect:1,
 			ancestry_path:1,
-			first_parent_only:1;
+			first_parent_only:1,
+			line_level_traverse:1,
+			full_line_diff:1;
 
 	/* Diff flags */
 	unsigned int	diff:1,
@@ -137,6 +143,9 @@ struct rev_info {
 	/* commit counts */
 	int count_left;
 	int count_right;
+	/* line level range that we are chasing */
+	struct decoration line_range;
+	struct decoration nontrivial_merge;
 };
 
 #define REV_TREE_SAME		0
@@ -193,4 +202,14 @@ enum commit_action {
 extern enum commit_action get_commit_action(struct rev_info *revs, struct commit *commit);
 extern enum commit_action simplify_commit(struct rev_info *revs, struct commit *commit);
 
+enum rewrite_result {
+	rewrite_one_ok,
+	rewrite_one_noparents,
+	rewrite_one_error
+};
+
+typedef enum rewrite_result (*rewrite_parent_fn_t)(struct rev_info *revs, struct commit **pp);
+
+extern int rewrite_parents(struct rev_info *revs, struct commit *commit,
+	rewrite_parent_fn_t rewrite_parent);
 #endif

t/t4301-log-line-single-history.sh

@@ -0,0 +1,685 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Bo Yang
+#
+
+test_description='Test git log -L with single line of history'
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/diff-lib.sh
+
+cat >path0 <<\EOF
+void func()
+{
+	int a = 0;
+	int b = 1;
+	int c;
+	c = a + b;
+}
+EOF
+
+cat >path1 <<\EOF
+void output()
+{
+	printf("hello world");
+}
+EOF
+
+test_expect_success 'add path0/path1 and commit.' '
+	git add path0 path1 &&
+	git commit -m "Base commit"
+'
+
+cat >path0 <<\EOF
+void func()
+{
+	int a = 10;
+	int b = 11;
+	int c;
+	c = a + b;
+}
+EOF
+
+cat >path1 <<\EOF
+void output()
+{
+	const char *str = "hello world!";
+	printf("%s", str);
+}
+EOF
+
+test_expect_success 'Change the 2,3 lines of path0 and path1.' '
+	git add path0 path1 &&
+	git commit -m "Change 2,3 lines of path0 and path1"
+'
+
+cat >path0 <<\EOF
+void func()
+{
+	int a = 10;
+	int b = 11;
+	int c;
+	c = 10 * (a + b);
+}
+EOF
+
+test_expect_success 'Change the 5th line of path0.' '
+	git add path0 &&
+	git commit -m "Change the 5th line of path0"
+'
+
+cat >path0 <<\EOF
+void func()
+{
+	int a = 10;
+	int b = 11;
+	printf("%d", a - b);
+}
+EOF
+
+test_expect_success 'Final change of path0.' '
+	git add path0 &&
+	git commit -m "Final change of path0"
+'
+
+cat >expected-path0 <<\EOF
+Final change of path0
+
+diff --git a/path0 b/path0
+index ccdf243..ccf8bcf 100644
+--- a/path0
++++ b/path0
+@@ -1,7 +1,6 @@
+ void func()
+ {
+ 	int a = 10;
+ 	int b = 11;
+-	int c;
+-	c = 10 * (a + b);
++	printf("%d", a - b);
+ }
+
+Change the 5th line of path0
+
+diff --git a/path0 b/path0
+index b0eb888..ccdf243 100644
+--- a/path0
++++ b/path0
+@@ -1,7 +1,7 @@
+ void func()
+ {
+ 	int a = 10;
+ 	int b = 11;
+ 	int c;
+-	c = a + b;
++	c = 10 * (a + b);
+ }
+
+Change 2,3 lines of path0 and path1
+
+diff --git a/path0 b/path0
+index fb33939..b0eb888 100644
+--- a/path0
++++ b/path0
+@@ -1,7 +1,7 @@
+ void func()
+ {
+-	int a = 0;
+-	int b = 1;
++	int a = 10;
++	int b = 11;
+ 	int c;
+ 	c = a + b;
+ }
+
+Base commit
+
+diff --git a/path0 b/path0
+new file mode 100644
+index 0000000..fb33939
+--- /dev/null
++++ b/path0
+@@ -0,0 +1,7 @@
++void func()
++{
++	int a = 0;
++	int b = 1;
++	int c;
++	c = a + b;
++}
+EOF
+
+cat >expected-path1 <<\EOF
+Change 2,3 lines of path0 and path1
+
+diff --git a/path1 b/path1
+index 52be2a5..cc54b12 100644
+--- a/path1
++++ b/path1
+@@ -1,4 +1,5 @@
+ void output()
+ {
+-	printf("hello world");
++	const char *str = "hello world!";
++	printf("%s", str);
+ }
+
+Base commit
+
+diff --git a/path1 b/path1
+new file mode 100644
+index 0000000..52be2a5
+--- /dev/null
++++ b/path1
+@@ -0,0 +1,4 @@
++void output()
++{
++	printf("hello world");
++}
+EOF
+
+cat >expected-pathall <<\EOF
+Final change of path0
+
+diff --git a/path0 b/path0
+index ccdf243..ccf8bcf 100644
+--- a/path0
++++ b/path0
+@@ -1,7 +1,6 @@
+ void func()
+ {
+ 	int a = 10;
+ 	int b = 11;
+-	int c;
+-	c = 10 * (a + b);
++	printf("%d", a - b);
+ }
+
+Change the 5th line of path0
+
+diff --git a/path0 b/path0
+index b0eb888..ccdf243 100644
+--- a/path0
++++ b/path0
+@@ -1,7 +1,7 @@
+ void func()
+ {
+ 	int a = 10;
+ 	int b = 11;
+ 	int c;
+-	c = a + b;
++	c = 10 * (a + b);
+ }
+
+Change 2,3 lines of path0 and path1
+
+diff --git a/path0 b/path0
+index fb33939..b0eb888 100644
+--- a/path0
++++ b/path0
+@@ -1,7 +1,7 @@
+ void func()
+ {
+-	int a = 0;
+-	int b = 1;
++	int a = 10;
++	int b = 11;
+ 	int c;
+ 	c = a + b;
+ }
+diff --git a/path1 b/path1
+index 52be2a5..cc54b12 100644
+--- a/path1
++++ b/path1
+@@ -1,4 +1,5 @@
+ void output()
+ {
+-	printf("hello world");
++	const char *str = "hello world!";
++	printf("%s", str);
+ }
+
+Base commit
+
+diff --git a/path0 b/path0
+new file mode 100644
+index 0000000..fb33939
+--- /dev/null
++++ b/path0
+@@ -0,0 +1,7 @@
++void func()
++{
++	int a = 0;
++	int b = 1;
++	int c;
++	c = a + b;
++}
+diff --git a/path1 b/path1
+new file mode 100644
+index 0000000..52be2a5
+--- /dev/null
++++ b/path1
+@@ -0,0 +1,4 @@
++void output()
++{
++	printf("hello world");
++}
+EOF
+
+cat >expected-linenum <<\EOF
+Change 2,3 lines of path0 and path1
+
+diff --git a/path0 b/path0
+index fb33939..b0eb888 100644
+--- a/path0
++++ b/path0
+@@ -2,3 +2,3 @@
+ {
+-	int a = 0;
+-	int b = 1;
++	int a = 10;
++	int b = 11;
+
+Base commit
+
+diff --git a/path0 b/path0
+new file mode 100644
+index 0000000..fb33939
+--- /dev/null
++++ b/path0
+@@ -0,0 +2,3 @@
++{
++	int a = 0;
++	int b = 1;
+EOF
+
+cat >expected-always <<\EOF
+Final change of path0
+
+diff --git a/path0 b/path0
+index ccdf243..ccf8bcf 100644
+--- a/path0
++++ b/path0
+@@ -2,3 +2,3 @@
+ {
+ 	int a = 10;
+ 	int b = 11;
+
+Change the 5th line of path0
+
+diff --git a/path0 b/path0
+index b0eb888..ccdf243 100644
+--- a/path0
++++ b/path0
+@@ -2,3 +2,3 @@
+ {
+ 	int a = 10;
+ 	int b = 11;
+
+Change 2,3 lines of path0 and path1
+
+diff --git a/path0 b/path0
+index fb33939..b0eb888 100644
+--- a/path0
++++ b/path0
+@@ -2,3 +2,3 @@
+ {
+-	int a = 0;
+-	int b = 1;
++	int a = 10;
++	int b = 11;
+
+Base commit
+
+diff --git a/path0 b/path0
+new file mode 100644
+index 0000000..fb33939
+--- /dev/null
++++ b/path0
+@@ -0,0 +2,3 @@
++{
++	int a = 0;
++	int b = 1;
+EOF
+
+test_expect_success 'Show the line level log of path0' '
+	git log --pretty=format:%s%n%b -L /func/,/^}/ path0 > current-path0
+'
+
+test_expect_success 'validate the path0 output.' '
+	test_cmp current-path0 expected-path0
+'
+
+test_expect_success 'Show the line level log of path1' '
+	git log --pretty=format:%s%n%b -L /output/,/^}/ path1 > current-path1
+'
+
+test_expect_success 'validate the path1 output.' '
+	test_cmp current-path1 expected-path1
+'
+
+test_expect_success 'Show the line level log of two files' '
+	git log --pretty=format:%s%n%b -L /func/,/^}/ path0 -L /output/,/^}/ path1 > current-pathall
+'
+
+test_expect_success 'validate the all path output.' '
+	test_cmp current-pathall expected-pathall
+'
+
+test_expect_success 'Test the line number argument' '
+	git log --pretty=format:%s%n%b -L 2,4 path0 > current-linenum
+'
+
+test_expect_success 'validate the line number output.' '
+	test_cmp current-linenum expected-linenum
+'
+test_expect_success 'Test the --full-line-diff option' '
+	git log --pretty=format:%s%n%b --full-line-diff -L 2,4 path0 > current-always
+'
+
+test_expect_success 'validate the --full-line-diff output.' '
+    test_cmp current-always expected-always
+'
+
+# Rerun all log with graph
+test_expect_success 'Show the line level log of path0 with --graph' '
+	git log --pretty=format:%s%n%b --graph -L /func/,/^}/ path0 > current-path0-graph
+'
+
+test_expect_success 'Show the line level log of path1 with --graph' '
+	git log --pretty=format:%s%n%b --graph -L /output/,/^}/ path1 > current-path1-graph
+'
+
+test_expect_success 'Show the line level log of two files with --graph' '
+	git log --pretty=format:%s%n%b --graph -L /func/,/^}/ path0 --graph -L /output/,/^}/ path1 > current-pathall-graph
+'
+
+test_expect_success 'Test the line number argument with --graph' '
+	git log --pretty=format:%s%n%b --graph -L 2,4 path0 > current-linenum-graph
+'
+
+test_expect_success 'Test the --full-line-diff option with --graph option' '
+	git log --pretty=format:%s%n%b --full-line-diff --graph -L 2,4 path0 > current-always-graph
+'
+
+cat > expected-path0-graph <<\EOF
+* Final change of path0
+| 
+| diff --git a/path0 b/path0
+| index ccdf243..ccf8bcf 100644
+| --- a/path0
+| +++ b/path0
+| @@ -1,7 +1,6 @@
+|  void func()
+|  {
+|  	int a = 10;
+|  	int b = 11;
+| -	int c;
+| -	c = 10 * (a + b);
+| +	printf("%d", a - b);
+|  }
+|  
+* Change the 5th line of path0
+| 
+| diff --git a/path0 b/path0
+| index b0eb888..ccdf243 100644
+| --- a/path0
+| +++ b/path0
+| @@ -1,7 +1,7 @@
+|  void func()
+|  {
+|  	int a = 10;
+|  	int b = 11;
+|  	int c;
+| -	c = a + b;
+| +	c = 10 * (a + b);
+|  }
+|  
+* Change 2,3 lines of path0 and path1
+| 
+| diff --git a/path0 b/path0
+| index fb33939..b0eb888 100644
+| --- a/path0
+| +++ b/path0
+| @@ -1,7 +1,7 @@
+|  void func()
+|  {
+| -	int a = 0;
+| -	int b = 1;
+| +	int a = 10;
+| +	int b = 11;
+|  	int c;
+|  	c = a + b;
+|  }
+|  
+* Base commit
+  
+  diff --git a/path0 b/path0
+  new file mode 100644
+  index 0000000..fb33939
+  --- /dev/null
+  +++ b/path0
+  @@ -0,0 +1,7 @@
+  +void func()
+  +{
+  +	int a = 0;
+  +	int b = 1;
+  +	int c;
+  +	c = a + b;
+  +}
+EOF
+
+cat > expected-path1-graph <<\EOF
+* Change 2,3 lines of path0 and path1
+| 
+| diff --git a/path1 b/path1
+| index 52be2a5..cc54b12 100644
+| --- a/path1
+| +++ b/path1
+| @@ -1,4 +1,5 @@
+|  void output()
+|  {
+| -	printf("hello world");
+| +	const char *str = "hello world!";
+| +	printf("%s", str);
+|  }
+|  
+* Base commit
+  
+  diff --git a/path1 b/path1
+  new file mode 100644
+  index 0000000..52be2a5
+  --- /dev/null
+  +++ b/path1
+  @@ -0,0 +1,4 @@
+  +void output()
+  +{
+  +	printf("hello world");
+  +}
+EOF
+
+cat > expected-pathall-graph <<\EOF
+* Final change of path0
+| 
+| diff --git a/path0 b/path0
+| index ccdf243..ccf8bcf 100644
+| --- a/path0
+| +++ b/path0
+| @@ -1,7 +1,6 @@
+|  void func()
+|  {
+|  	int a = 10;
+|  	int b = 11;
+| -	int c;
+| -	c = 10 * (a + b);
+| +	printf("%d", a - b);
+|  }
+|  
+* Change the 5th line of path0
+| 
+| diff --git a/path0 b/path0
+| index b0eb888..ccdf243 100644
+| --- a/path0
+| +++ b/path0
+| @@ -1,7 +1,7 @@
+|  void func()
+|  {
+|  	int a = 10;
+|  	int b = 11;
+|  	int c;
+| -	c = a + b;
+| +	c = 10 * (a + b);
+|  }
+|  
+* Change 2,3 lines of path0 and path1
+| 
+| diff --git a/path0 b/path0
+| index fb33939..b0eb888 100644
+| --- a/path0
+| +++ b/path0
+| @@ -1,7 +1,7 @@
+|  void func()
+|  {
+| -	int a = 0;
+| -	int b = 1;
+| +	int a = 10;
+| +	int b = 11;
+|  	int c;
+|  	c = a + b;
+|  }
+| diff --git a/path1 b/path1
+| index 52be2a5..cc54b12 100644
+| --- a/path1
+| +++ b/path1
+| @@ -1,4 +1,5 @@
+|  void output()
+|  {
+| -	printf("hello world");
+| +	const char *str = "hello world!";
+| +	printf("%s", str);
+|  }
+|  
+* Base commit
+  
+  diff --git a/path0 b/path0
+  new file mode 100644
+  index 0000000..fb33939
+  --- /dev/null
+  +++ b/path0
+  @@ -0,0 +1,7 @@
+  +void func()
+  +{
+  +	int a = 0;
+  +	int b = 1;
+  +	int c;
+  +	c = a + b;
+  +}
+  diff --git a/path1 b/path1
+  new file mode 100644
+  index 0000000..52be2a5
+  --- /dev/null
+  +++ b/path1
+  @@ -0,0 +1,4 @@
+  +void output()
+  +{
+  +	printf("hello world");
+  +}
+EOF
+
+cat > expected-linenum-graph <<\EOF
+* Change 2,3 lines of path0 and path1
+| 
+| diff --git a/path0 b/path0
+| index fb33939..b0eb888 100644
+| --- a/path0
+| +++ b/path0
+| @@ -2,3 +2,3 @@
+|  {
+| -	int a = 0;
+| -	int b = 1;
+| +	int a = 10;
+| +	int b = 11;
+|  
+* Base commit
+  
+  diff --git a/path0 b/path0
+  new file mode 100644
+  index 0000000..fb33939
+  --- /dev/null
+  +++ b/path0
+  @@ -0,0 +2,3 @@
+  +{
+  +	int a = 0;
+  +	int b = 1;
+EOF
+
+cat > expected-always-graph <<\EOF
+* Final change of path0
+| 
+| diff --git a/path0 b/path0
+| index ccdf243..ccf8bcf 100644
+| --- a/path0
+| +++ b/path0
+| @@ -2,3 +2,3 @@
+|  {
+|  	int a = 10;
+|  	int b = 11;
+|  
+* Change the 5th line of path0
+| 
+| diff --git a/path0 b/path0
+| index b0eb888..ccdf243 100644
+| --- a/path0
+| +++ b/path0
+| @@ -2,3 +2,3 @@
+|  {
+|  	int a = 10;
+|  	int b = 11;
+|  
+* Change 2,3 lines of path0 and path1
+| 
+| diff --git a/path0 b/path0
+| index fb33939..b0eb888 100644
+| --- a/path0
+| +++ b/path0
+| @@ -2,3 +2,3 @@
+|  {
+| -	int a = 0;
+| -	int b = 1;
+| +	int a = 10;
+| +	int b = 11;
+|  
+* Base commit
+  
+  diff --git a/path0 b/path0
+  new file mode 100644
+  index 0000000..fb33939
+  --- /dev/null
+  +++ b/path0
+  @@ -0,0 +2,3 @@
+  +{
+  +	int a = 0;
+  +	int b = 1;
+EOF
+
+test_expect_success 'validate the path0 output.' '
+	test_cmp current-path0-graph expected-path0-graph
+'
+
+test_expect_success 'validate the path1 output.' '
+	test_cmp current-path1-graph expected-path1-graph
+'
+
+test_expect_success 'validate the all path output.' '
+	test_cmp current-pathall-graph expected-pathall-graph
+'
+
+test_expect_success 'validate graph output' '
+	test_cmp current-linenum-graph expected-linenum-graph
+'
+
+test_expect_success 'validate --full-line-diff output' '
+	test_cmp current-always-graph expected-always-graph
+'
+
+test_done

t/t4302-log-line-merge-history.sh

@@ -0,0 +1,174 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Bo Yang
+#
+
+test_description='Test git log -L with merge commit'
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/diff-lib.sh
+
+cat >path0 <<\EOF
+void func()
+{
+	printf("hello");
+}
+EOF
+
+test_expect_success 'Add path0 and commit.' '
+	git add path0 &&
+	git commit -m "Base commit"
+'
+
+cat >path0 <<\EOF
+void func()
+{
+	printf("hello earth");
+}
+EOF
+
+test_expect_success 'Change path0 in master.' '
+	git add path0 &&
+	git commit -m "Change path0 in master"
+'
+
+test_expect_success 'Make a new branch from the base commit' '
+	git checkout -b feature master^
+'
+
+cat >path0 <<\EOF
+void func()
+{
+	print("hello moon");
+}
+EOF
+
+test_expect_success 'Change path0 in feature.' '
+	git add path0 &&
+	git commit -m "Change path0 in feature"
+'
+
+test_expect_success 'Merge the master to feature' '
+	! git merge master
+'
+
+cat >path0 <<\EOF
+void func()
+{
+	printf("hello earth and moon");
+}
+EOF
+
+test_expect_success 'Resolve the conflict' '
+	git add path0 &&
+	git commit -m "Merge two branches"
+'
+
+test_expect_success 'Show the line level log of path0' '
+	git log --pretty=format:%s%n%b -L /func/,/^}/ path0 > current
+'
+
+cat >expected <<\EOF
+Merge two branches
+
+nontrivial merge found
+path0
+@@ 3,1 @@
+ 	printf("hello earth and moon");
+
+
+Change path0 in master
+
+diff --git a/path0 b/path0
+index 56aeee5..11e66c5 100644
+--- a/path0
++++ b/path0
+@@ -1,4 +1,4 @@
+ void func()
+ {
+-	printf("hello");
++	printf("hello earth");
+ }
+
+Change path0 in feature
+
+diff --git a/path0 b/path0
+index 56aeee5..258fced 100644
+--- a/path0
++++ b/path0
+@@ -1,4 +1,4 @@
+ void func()
+ {
+-	printf("hello");
++	print("hello moon");
+ }
+
+Base commit
+
+diff --git a/path0 b/path0
+new file mode 100644
+index 0000000..56aeee5
+--- /dev/null
++++ b/path0
+@@ -0,0 +1,4 @@
++void func()
++{
++	printf("hello");
++}
+EOF
+
+cat > expected-graph <<\EOF
+*   Merge two branches
+|\  
+| | 
+| | nontrivial merge found
+| | path0
+| | @@ 3,1 @@
+| |  	printf("hello earth and moon");
+| | 
+| |   
+| * Change path0 in master
+| | 
+| | diff --git a/path0 b/path0
+| | index 56aeee5..11e66c5 100644
+| | --- a/path0
+| | +++ b/path0
+| | @@ -3,1 +3,1 @@
+| | -	printf("hello");
+| | +	printf("hello earth");
+| |   
+* | Change path0 in feature
+|/  
+|   
+|   diff --git a/path0 b/path0
+|   index 56aeee5..258fced 100644
+|   --- a/path0
+|   +++ b/path0
+|   @@ -3,1 +3,1 @@
+|   -	printf("hello");
+|   +	print("hello moon");
+|  
+* Base commit
+  
+  diff --git a/path0 b/path0
+  new file mode 100644
+  index 0000000..56aeee5
+  --- /dev/null
+  +++ b/path0
+  @@ -0,0 +3,1 @@
+  +	printf("hello");
+EOF
+
+test_expect_success 'Show the line log of the 2 line of path0 with graph' '
+	git log --pretty=format:%s%n%b --graph -L 3,+1 path0 > current-graph
+'
+
+test_expect_success 'validate the output.' '
+	test_cmp current expected
+'
+
+test_expect_success 'validate the graph output.' '
+	test_cmp current-graph expected-graph
+'
+
+test_done