Merge branch 'range-diff'

This takes an early version of the `range-diff` branch, for the benefit
of GitGitGadget.

Signed-off-by: Johannes Schindelin <[email protected]>

.gitignore

@@ -112,6 +112,7 @@
 /git-pull
 /git-push
 /git-quiltimport
+/git-range-diff
 /git-read-tree
 /git-rebase
 /git-rebase--am

Documentation/git-range-diff.txt

@@ -0,0 +1,235 @@
+git-range-diff(1)
+==================
+
+NAME
+----
+git-range-diff - Compare two commit ranges (e.g. two versions of a branch)
+
+SYNOPSIS
+--------
+[verse]
+'git range-diff' [--color=[<when>]] [--no-color] [<diff-options>]
+	[--dual-color] [--creation-factor=<factor>]
+	( <range1> <range2> | <rev1>...<rev2> | <base> <rev1> <rev2> )
+
+DESCRIPTION
+-----------
+
+This command shows the differences between two versions of a patch
+series, or more generally, two commit ranges (ignoring merges).
+
+To that end, it first finds pairs of commits from both commit ranges
+that correspond with each other. Two commits are said to correspond when
+the diff between their patches (i.e. the author information, the commit
+message and the commit diff) is reasonably small compared to the
+patches' size. See ``Algorithm` below for details.
+
+Finally, the list of matching commits is shown in the order of the
+second commit range, with unmatched commits being inserted just after
+all of their ancestors have been shown.
+
+
+OPTIONS
+-------
+--dual-color::
+	When the commit diffs differ, recreate the original diffs'
+	coloring, and add outer -/+ diff markers with the *background*
+	being red/green to make it easier to see e.g. when there was a
+	change in what exact lines were added.
+
+--creation-factor=<percent>::
+	Set the creation/deletion cost fudge factor to `<percent>`.
+	Defaults to 60. Try a larger value if `git range-diff` erroneously
+	considers a large change a total rewrite (deletion of one commit
+	and addition of another), and a smaller one in the reverse case.
+	See the ``Algorithm`` section below for an explanation why this is
+	needed.
+
+<range1> <range2>::
+	Compare the commits specified by the two ranges, where
+	`<range1>` is considered an older version of `<range2>`.
+
+<rev1>...<rev2>::
+	Equivalent to passing `<rev2>..<rev1>` and `<rev1>..<rev2>`.
+
+<base> <rev1> <rev2>::
+	Equivalent to passing `<base>..<rev1>` and `<base>..<rev2>`.
+	Note that `<base>` does not need to be the exact branch point
+	of the branches. Example: after rebasing a branch `my-topic`,
+	`git range-diff my-topic@{u} my-topic@{1} my-topic` would
+	show the differences introduced by the rebase.
+
+`git range-diff` also accepts the regular diff options (see
+linkgit:git-diff[1]), most notably the `--color=[<when>]` and
+`--no-color` options. These options are used when generating the "diff
+between patches", i.e. to compare the author, commit message and diff of
+corresponding old/new commits. There is currently no means to tweak the
+diff options passed to `git log` when generating those patches.
+
+
+CONFIGURATION
+-------------
+This command uses the `diff.color.*` and `pager.range-diff` settings
+(the latter is on by default).
+See linkgit:git-config[1].
+
+
+EXAMPLES
+--------
+
+When a rebase required merge conflicts to be resolved, compare the changes
+introduced by the rebase directly afterwards using:
+
+------------
+$ git range-diff @{u} @{1} @
+------------
+
+
+A typical output of `git range-diff` would look like this:
+
+------------
+-:  ------- > 1:  0ddba11 Prepare for the inevitable!
+1:  c0debee = 2:  cab005e Add a helpful message at the start
+2:  f00dbal ! 3:  decafe1 Describe a bug
+    @@ -1,3 +1,3 @@
+     Author: A U Thor <[email protected]>
+
+    -TODO: Describe a bug
+    +Describe a bug
+    @@ -324,5 +324,6
+      This is expected.
+
+    -+What is unexpected is that it will also crash.
+    ++Unexpectedly, it also crashes. This is a bug, and the jury is
+    ++still out there how to fix it best. See ticket #314 for details.
+
+      Contact
+3:  bedead < -:  ------- TO-UNDO
+------------
+
+In this example, there are 3 old and 3 new commits, where the developer
+removed the 3rd, added a new one before the first two, and modified the
+commit message of the 2nd commit as well its diff.
+
+When the output goes to a terminal, it is color-coded by default, just
+like regular `git diff`'s output. In addition, the first line (adding a
+commit) is green, the last line (deleting a commit) is red, the second
+line (with a perfect match) is yellow like the commit header of `git
+show`'s output, and the third line colors the old commit red, the new
+one green and the rest like `git show`'s commit header.
+
+The color-coded diff is actually a bit hard to read, though, as it
+colors the entire lines red or green. The line that added "What is
+unexpected" in the old commit, for example, is completely red, even if
+the intent of the old commit was to add something.
+
+To help with that, use the `--dual-color` mode. In this mode, the diff
+of diffs will retain the original diff colors, and prefix the lines with
+-/+ markers that have their *background* red or green, to make it more
+obvious that they describe how the diff itself changed.
+
+
+Algorithm
+---------
+
+The general idea is this: we generate a cost matrix between the commits
+in both commit ranges, then solve the least-cost assignment.
+
+To avoid false positives (e.g. when a patch has been removed, and an
+unrelated patch has been added between two iterations of the same patch
+series), the cost matrix is extended to allow for that, by adding
+fixed-cost entries for wholesale deletes/adds.
+
+Example: Let commits `1--2` be the first iteration of a patch series and
+`A--C` the second iteration. Let's assume that `A` is a cherry-pick of
+`2,` and `C` is a cherry-pick of `1` but with a small modification (say,
+a fixed typo). Visualize the commits as a bipartite graph:
+
+------------
+    1            A
+
+    2            B
+
+		 C
+------------
+
+We are looking for a "best" explanation of the new series in terms of
+the old one. We can represent an "explanation" as an edge in the graph:
+
+
+------------
+    1            A
+	       /
+    2 --------'  B
+
+		 C
+------------
+
+This explanation comes for "free" because there was no change. Similarly
+`C` could be explained using `1`, but that comes at some cost c>0
+because of the modification:
+
+------------
+    1 ----.      A
+	  |    /
+    2 ----+---'  B
+	  |
+	  `----- C
+	  c>0
+------------
+
+In mathematical terms, what we are looking for is some sort of a minimum
+cost bipartite matching; `1` is matched to `C` at some cost, etc. The
+underlying graph is in fact a complete bipartite graph; the cost we
+associate with every edge is the size of the diff between the two
+commits' patches. To explain also new commits, we introduce dummy nodes
+on both sides:
+
+------------
+    1 ----.      A
+	  |    /
+    2 ----+---'  B
+	  |
+    o     `----- C
+	  c>0
+    o            o
+
+    o            o
+------------
+
+The cost of an edge `o--C` is the size of `C`'s diff, modified by a
+fudge factor that should be smaller than 100%. The cost of an edge
+`o--o` is free. The fudge factor is necessary because even if `1` and
+`C` have nothing in common, they may still share a few empty lines and
+such, possibly making the assignment `1--C`, `o--o` slightly cheaper
+than `1--o`, `o--C` even if `1` and `C` have nothing in common. With the
+fudge factor we require a much larger common part to consider patches as
+corresponding.
+
+The overall time needed to compute this algorithm is the time needed to
+compute n+m commit diffs and then n*m diffs of patches, plus the time
+needed to compute the least-cost assigment between n and m diffs. Git
+uses an implementation of the Jonker-Volgenant algorithm to solve the
+assignment problem, which has cubic runtime complexity. The matching
+found in this case will look like this:
+
+------------
+    1 ----.      A
+	  |    /
+    2 ----+---'  B
+       .--+-----'
+    o -'  `----- C
+	  c>0
+    o ---------- o
+
+    o ---------- o
+------------
+
+
+SEE ALSO
+--------
+linkgit:git-log[1]
+
+GIT
+---
+Part of the linkgit:git[1] suite

Makefile

@@ -853,6 +853,7 @@ LIB_OBJS += gpg-interface.o
 LIB_OBJS += graph.o
 LIB_OBJS += grep.o
 LIB_OBJS += hashmap.o
+LIB_OBJS += linear-assignment.o
 LIB_OBJS += help.o
 LIB_OBJS += hex.o
 LIB_OBJS += ident.o
@@ -903,6 +904,7 @@ LIB_OBJS += progress.o
 LIB_OBJS += prompt.o
 LIB_OBJS += protocol.o
 LIB_OBJS += quote.o
+LIB_OBJS += range-diff.o
 LIB_OBJS += reachable.o
 LIB_OBJS += read-cache.o
 LIB_OBJS += reflog-walk.o
@@ -1037,6 +1039,7 @@ BUILTIN_OBJS += builtin/prune-packed.o
 BUILTIN_OBJS += builtin/prune.o
 BUILTIN_OBJS += builtin/pull.o
 BUILTIN_OBJS += builtin/push.o
+BUILTIN_OBJS += builtin/range-diff.o
 BUILTIN_OBJS += builtin/read-tree.o
 BUILTIN_OBJS += builtin/rebase--helper.o
 BUILTIN_OBJS += builtin/receive-pack.o

builtin.h

@@ -200,6 +200,7 @@ extern int cmd_prune(int argc, const char **argv, const char *prefix);
 extern int cmd_prune_packed(int argc, const char **argv, const char *prefix);
 extern int cmd_pull(int argc, const char **argv, const char *prefix);
 extern int cmd_push(int argc, const char **argv, const char *prefix);
+extern int cmd_range_diff(int argc, const char **argv, const char *prefix);
 extern int cmd_read_tree(int argc, const char **argv, const char *prefix);
 extern int cmd_rebase__helper(int argc, const char **argv, const char *prefix);
 extern int cmd_receive_pack(int argc, const char **argv, const char *prefix);

builtin/range-diff.c

@@ -0,0 +1,102 @@
+#include "cache.h"
+#include "builtin.h"
+#include "parse-options.h"
+#include "range-diff.h"
+#include "config.h"
+
+static const char * const builtin_range_diff_usage[] = {
+N_("git range-diff [<options>] <old-base>..<old-tip> <new-base>..<new-tip>"),
+N_("git range-diff [<options>] <old-tip>...<new-tip>"),
+N_("git range-diff [<options>] <base> <old-tip> <new-tip>"),
+NULL
+};
+
+static struct strbuf *output_prefix_cb(struct diff_options *opt, void *data)
+{
+	return data;
+}
+
+int cmd_range_diff(int argc, const char **argv, const char *prefix)
+{
+	int creation_factor = 60;
+	struct diff_options diffopt = { NULL };
+	int dual_color = 0;
+	struct option options[] = {
+		OPT_INTEGER(0, "creation-factor", &creation_factor,
+			    N_("Percentage by which creation is weighted")),
+		OPT_BOOL(0, "dual-color", &dual_color,
+			    N_("color both diff and diff-between-diffs")),
+		OPT_END()
+	};
+	int i, j, res = 0;
+	struct strbuf four_spaces = STRBUF_INIT;
+	struct strbuf range1 = STRBUF_INIT, range2 = STRBUF_INIT;
+
+	git_config(git_diff_ui_config, NULL);
+
+	diff_setup(&diffopt);
+	diffopt.output_format = DIFF_FORMAT_PATCH;
+	diffopt.flags.suppress_diff_headers = 1;
+	diffopt.output_prefix = output_prefix_cb;
+	strbuf_addstr(&four_spaces, "    ");
+	diffopt.output_prefix_data = &four_spaces;
+
+	argc = parse_options(argc, argv, NULL, options,
+			builtin_range_diff_usage, PARSE_OPT_KEEP_UNKNOWN);
+
+	for (i = j = 0; i < argc; i++) {
+		int c = diff_opt_parse(&diffopt, argv + i, argc - i, prefix);
+
+		if (!c)
+			argv[j++] = argv[i];
+	}
+	argc = j;
+	diff_setup_done(&diffopt);
+
+	if (dual_color) {
+		diffopt.use_color = 1;
+		diffopt.flags.dual_color_diffed_diffs = 1;
+	}
+
+	if (argc == 2) {
+		if (!strstr(argv[0], ".."))
+			warning(_("no .. in range: '%s'"), argv[0]);
+		strbuf_addstr(&range1, argv[0]);
+
+		if (!strstr(argv[1], ".."))
+			warning(_("no .. in range: '%s'"), argv[1]);
+		strbuf_addstr(&range2, argv[1]);
+	} else if (argc == 3) {
+		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
+		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
+	} else if (argc == 1) {
+		const char *b = strstr(argv[0], "..."), *a = argv[0];
+		int a_len;
+
+		if (!b)
+			die(_("single arg format requires a symmetric range"));
+
+		a_len = (int)(b - a);
+		if (!a_len) {
+			a = "HEAD";
+			a_len = strlen(a);
+		}
+		b += 3;
+		if (!*b)
+			b = "HEAD";
+		strbuf_addf(&range1, "%s..%.*s", b, a_len, a);
+		strbuf_addf(&range2, "%.*s..%s", a_len, a, b);
+	} else {
+		error(_("need two commit ranges"));
+		usage_with_options(builtin_range_diff_usage, options);
+	}
+
+	res = show_range_diff(range1.buf, range2.buf, creation_factor,
+			      &diffopt);
+
+	strbuf_release(&range1);
+	strbuf_release(&range2);
+	strbuf_release(&four_spaces);
+
+	return res;
+}

color.h

@@ -44,6 +44,7 @@ struct strbuf;
 #define GIT_COLOR_BG_CYAN	"\033[46m"
 #define GIT_COLOR_FAINT		"\033[2m"
 #define GIT_COLOR_FAINT_ITALIC	"\033[2;3m"
+#define GIT_COLOR_REVERSE	"\033[7m"
 
 /* A special value meaning "no color selected" */
 #define GIT_COLOR_NIL "NIL"

command-list.txt

@@ -103,6 +103,7 @@ git-prune-packed                        plumbingmanipulators
 git-pull                                mainporcelain           remote
 git-push                                mainporcelain           remote
 git-quiltimport                         foreignscminterface
+git-range-diff                          mainporcelain
 git-read-tree                           plumbingmanipulators
 git-rebase                              mainporcelain           history
 git-receive-pack                        synchelpers