Merge branch 'sb/diff-color-move'

"git diff" has been taught to optionally paint new lines that are
the same as deleted lines elsewhere differently from genuinely new
lines.

* sb/diff-color-move: (25 commits)
  diff: document the new --color-moved setting
  diff.c: add dimming to moved line detection
  diff.c: color moved lines differently, plain mode
  diff.c: color moved lines differently
  diff.c: buffer all output if asked to
  diff.c: emit_diff_symbol learns about DIFF_SYMBOL_SUMMARY
  diff.c: emit_diff_symbol learns about DIFF_SYMBOL_STAT_SEP
  diff.c: convert word diffing to use emit_diff_symbol
  diff.c: convert show_stats to use emit_diff_symbol
  diff.c: convert emit_binary_diff_body to use emit_diff_symbol
  submodule.c: migrate diff output to use emit_diff_symbol
  diff.c: emit_diff_symbol learns DIFF_SYMBOL_REWRITE_DIFF
  diff.c: emit_diff_symbol learns about DIFF_SYMBOL_BINARY_FILES
  diff.c: emit_diff_symbol learns DIFF_SYMBOL_HEADER
  diff.c: emit_diff_symbol learns DIFF_SYMBOL_FILEPAIR_{PLUS, MINUS}
  diff.c: emit_diff_symbol learns DIFF_SYMBOL_CONTEXT_INCOMPLETE
  diff.c: emit_diff_symbol learns DIFF_SYMBOL_WORDS[_PORCELAIN]
  diff.c: migrate emit_line_checked to use emit_diff_symbol
  diff.c: emit_diff_symbol learns DIFF_SYMBOL_NO_LF_EOF
  diff.c: emit_diff_symbol learns DIFF_SYMBOL_CONTEXT_FRAGINFO
  ...

Author: gitster

Documentation/config.txt

@@ -1077,14 +1077,25 @@ This does not affect linkgit:git-format-patch[1] or the
 'git-diff-{asterisk}' plumbing commands.  Can be overridden on the
 command line with the `--color[=<when>]` option.
 
+diff.colorMoved::
+	If set to either a valid `<mode>` or a true value, moved lines
+	in a diff are colored differently, for details of valid modes
+	see '--color-moved' in linkgit:git-diff[1]. If simply set to
+	true the default color mode will be used. When set to false,
+	moved lines are not colored.
+
 color.diff.<slot>::
 	Use customized color for diff colorization.  `<slot>` specifies
 	which part of the patch to use the specified color, and is one
 	of `context` (context text - `plain` is a historical synonym),
 	`meta` (metainformation), `frag`
 	(hunk header), 'func' (function in hunk header), `old` (removed lines),
-	`new` (added lines), `commit` (commit headers), or `whitespace`
-	(highlighting whitespace errors).
+	`new` (added lines), `commit` (commit headers), `whitespace`
+	(highlighting whitespace errors), `oldMoved` (deleted lines),
+	`newMoved` (added lines), `oldMovedDimmed`, `oldMovedAlternative`,
+	`oldMovedAlternativeDimmed`, `newMovedDimmed`, `newMovedAlternative`
+	and `newMovedAlternativeDimmed` (See the '<mode>'
+	setting of '--color-moved' in linkgit:git-diff[1] for details).
 
 color.decorate.<slot>::
 	Use customized color for 'git log --decorate' output.  `<slot>` is one

Documentation/diff-options.txt

@@ -231,6 +231,42 @@ ifdef::git-diff[]
 endif::git-diff[]
 	It is the same as `--color=never`.
 
+--color-moved[=<mode>]::
+	Moved lines of code are colored differently.
+ifdef::git-diff[]
+	It can be changed by the `diff.colorMoved` configuration setting.
+endif::git-diff[]
+	The <mode> defaults to 'no' if the option is not given
+	and to 'zebra' if the option with no mode is given.
+	The mode must be one of:
++
+--
+no::
+	Moved lines are not highlighted.
+default::
+	Is a synonym for `zebra`. This may change to a more sensible mode
+	in the future.
+plain::
+	Any line that is added in one location and was removed
+	in another location will be colored with 'color.diff.newMoved'.
+	Similarly 'color.diff.oldMoved' will be used for removed lines
+	that are added somewhere else in the diff. This mode picks up any
+	moved line, but it is not very useful in a review to determine
+	if a block of code was moved without permutation.
+zebra::
+	Blocks of moved code are detected greedily. The detected blocks are
+	painted using either the 'color.diff.{old,new}Moved' color or
+	'color.diff.{old,new}MovedAlternative'. The change between
+	the two colors indicates that a new block was detected. If there
+	are fewer than 3 adjacent moved lines, they are not marked up
+	as moved, but the regular colors 'color.diff.{old,new}' will be
+	used.
+dimmed_zebra::
+	Similar to 'zebra', but additional dimming of uninteresting parts
+	of moved code is performed. The bordering lines of two adjacent
+	blocks are considered interesting, the rest is uninteresting.
+--
+
 --word-diff[=<mode>]::
 	Show a word diff, using the <mode> to delimit changed words.
 	By default, words are delimited by whitespace; see

cache.h

@@ -1955,6 +1955,8 @@ void shift_tree_by(const struct object_id *, const struct object_id *, struct ob
 #define WS_TRAILING_SPACE      (WS_BLANK_AT_EOL|WS_BLANK_AT_EOF)
 #define WS_DEFAULT_RULE (WS_TRAILING_SPACE|WS_SPACE_BEFORE_TAB|8)
 #define WS_TAB_WIDTH_MASK        077
+/* All WS_* -- when extended, adapt diff.c emit_symbol */
+#define WS_RULE_MASK           07777
 extern unsigned whitespace_rule_cfg;
 extern unsigned whitespace_rule(const char *);
 extern unsigned parse_whitespace_rule(const char *);

color.h

@@ -42,6 +42,8 @@ struct strbuf;
 #define GIT_COLOR_BG_BLUE	"\033[44m"
 #define GIT_COLOR_BG_MAGENTA	"\033[45m"
 #define GIT_COLOR_BG_CYAN	"\033[46m"
+#define GIT_COLOR_FAINT		"\033[2m"
+#define GIT_COLOR_FAINT_ITALIC	"\033[2;3m"
 
 /* A special value meaning "no color selected" */
 #define GIT_COLOR_NIL "NIL"