Add support for hiding diff signs (leading + and -)

The `+` and `-` signs in diff views can be removed by setting the new
option `diff-hide-signs`. When set, only the color of the lines
distinguishes added, removed and context lines.

Empty added or removed lines are indicated by a space in column 0 with
the "diff highlight" colors which has the `reverse` property by default.

Closes #855

doc/tigrc.5.adoc

@@ -270,6 +270,16 @@ The following variables can be set:
 
 	Number of context lines to show for diffs.
 
+'diff-hide-signs' (bool)::
+
+	Hide the leading `+` and `-` signs in diff output. Copy-paste of lines
+	from the diff view may be aided by this option. Enabling this only makes
+	sense when coloring is used to distinguish added and removed lines.
+	Removed and added lines are indicated in the first column by a space
+	highlighted by the color `diff-add-highlight` or `diff-del-highlight`,
+	respectively. Keeping the `standout` (reverse) property set for these is
+	suggested, as white space is otherwise invisible. Off by default.
+
 'diff-highlight' (mixed)::
 
 	Whether to highlight diffs using Git's 'diff-highlight' program. Defaults

include/tig/options.h

@@ -37,6 +37,7 @@ typedef struct view_column *view_settings;
 	_(commit_order,			enum commit_order,	VIEW_LOG_LIKE) \
 	_(diff_context,			int,			VIEW_DIFF_LIKE) \
 	_(diff_noprefix,		bool,			VIEW_NO_FLAGS) \
+	_(diff_hide_signs,		bool,			VIEW_NO_FLAGS) \
 	_(diff_options,			const char **,		VIEW_DIFF_LIKE) \
 	_(diff_highlight,		const char *,		VIEW_DIFF_LIKE) \
 	_(diff_view,			view_settings,		VIEW_NO_FLAGS) \

src/draw.c

@@ -75,7 +75,25 @@ draw_chars(struct view *view, enum line_type type, const char *string, int lengt
 
 	set_view_attr(view, type);
 	if (len > 0)
-		waddnstr(view->win, string, len);
+	{
+		if (opt_diff_hide_signs &&
+		    view->col == 0      &&
+		    (type == LINE_DIFF_ADD || type == LINE_DIFF_DEL)
+		   ) {
+			/* Mark first column by color-only for add/del line */
+			if (type == LINE_DIFF_ADD)
+				set_view_attr(view, LINE_DIFF_ADD_HIGHLIGHT);
+			else if (type == LINE_DIFF_DEL)
+				set_view_attr(view, LINE_DIFF_DEL_HIGHLIGHT);
+			waddnstr(view->win, " ", 1);
+
+			/* Add the actual diff line */
+			set_view_attr(view, type);
+			waddnstr(view->win, string+1, len-1);
+		} else {
+			waddnstr(view->win, string, len);
+		}
+	}
 
 	if (trimmed && use_tilde) {
 		set_view_attr(view, LINE_DELIMITER);

test/diff/diff-hide-signs-test

@@ -0,0 +1,48 @@
+#!/bin/sh
+
+. libtest.sh
+. libgit.sh
+
+tigrc <<EOF
+set diff-hide-signs = true
+EOF
+
+steps '
+	:save-display diff-hide-signs.screen
+'
+
+in_work_dir create_repo_from_tgz "$base_dir/files/scala-js-benchmarks.tgz"
+
+test_tig show master^
+
+assert_equals 'diff-hide-signs.screen' <<EOF
+commit a1dcf1aaa11470978db1d5d8bcf9e16201eb70ff
+Author:     Jonas Fonseca <[email protected]>
+AuthorDate: Sat Mar 1 15:59:02 2014 -0500
+Commit:     Jonas Fonseca <[email protected]>
+CommitDate: Sat Mar 1 15:59:02 2014 -0500
+
+    Add type parameter for js.Dynamic
+---
+ common/src/main/scala/org/scalajs/benchmark/Benchmark.scala | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/common/src/main/scala/org/scalajs/benchmark/Benchmark.scala b/commo
+index 65f914a..3aa4320 100644
+--- a/common/src/main/scala/org/scalajs/benchmark/Benchmark.scala
++++ b/common/src/main/scala/org/scalajs/benchmark/Benchmark.scala
+@@ -15,7 +15,7 @@ object Benchmark {
+   val benchmarks = js.Array[Benchmark]()
+   val benchmarkApps = js.Array[BenchmarkApp]()
+
+   val global = js.Dynamic.global.asInstanceOf[js.Dictionary]
+   val global = js.Dynamic.global.asInstanceOf[js.Dictionary[js.Any]]
+   global("runScalaJSBenchmarks") = runBenchmarks _
+   global("initScalaJSBenchmarkApps") = initBenchmarkApps _
+
+
+
+
+
+[diff] a1dcf1aaa11470978db1d5d8bcf9e16201eb70ff - line 1 of 24              100%
+EOF

tigrc

@@ -114,6 +114,7 @@ set show-notes			= yes		# When non-bool passed as `--show-notes=...` (diff)
 #set diff-options		= -C		# User-defined options for `tig show` (git-diff)
 #set diff-highlight		= true		# String (or bool): Path to diff-highlight script,
 						#                   defaults to `diff-highlight`.
+set diff-hide-signs		= no		# Hide diff signs (+ and -) at the start of diff lines
 #set blame-options		= -C -C -C	# User-defined options for `tig blame` (git-blame)
 #set log-options		= --pretty=raw	# User-defined options for `tig log` (git-log)
 #set main-options		= -n 1000	# User-defined options for `tig` (git-log)