Re: [PATCH 2/4] diff.c: add --output-indicator-{new, old, context}

It could also be useful for experimentation in new patch formats, i.e.
we could teach git to emit moved lines with lines other than +/-.

Signed-off-by: Stefan Beller <redacted>
---
 diff.c | 21 +++++++++++++++++----
 diff.h |  5 +++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/diff.c b/diff.c
index b3cb73eb69a..b75eb085cb3 100644
--- a/diff.c
+++ b/diff.c

@@ -1237,7 +1237,7 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
 					 struct emitted_diff_symbol *eds)
 {
 	static const char *nneof = " No newline at end of file\n";
-	const char *context, *reset, *set, *set_sign, *meta, *fraginfo;
+	const char *context, *reset, *set, *set_sign, *meta, *fraginfo, *first;
 	struct strbuf sb = STRBUF_INIT;
 
 	enum diff_symbol s = eds->s;

@@ -1288,7 +1288,9 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
 			else if (c == '-')
 				set = diff_get_color_opt(o, DIFF_FILE_OLD);
 		}
-		emit_line_ws_markup(o, set_sign, set, reset, " ", line, len,
+		first = o->output_indicators[OI_CONTEXT] ?
+			o->output_indicators[OI_CONTEXT] : " ";
+		emit_line_ws_markup(o, set_sign, set, reset, first, line, len,

 				    flags & (DIFF_SYMBOL_CONTENT_WS_MASK), 0);
 		break;
 	case DIFF_SYMBOL_PLUS:

@@ -1331,7 +1333,10 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
 				set = diff_get_color_opt(o, DIFF_CONTEXT_BOLD);
 			flags &= ~DIFF_SYMBOL_CONTENT_WS_MASK;
 		}
-		emit_line_ws_markup(o, set_sign, set, reset, "+", line, len,
+
+		first = o->output_indicators[OI_NEW] ?
+			o->output_indicators[OI_NEW] : "+";
+		emit_line_ws_markup(o, set_sign, set, reset, first, line, len,
 				    flags & DIFF_SYMBOL_CONTENT_WS_MASK,
 				    flags & DIFF_SYMBOL_CONTENT_BLANK_LINE_EOF);
 		break;

@@ -1374,7 +1379,9 @@ static void emit_diff_symbol_from_struct(struct diff_options *o,
 			else
 				set = diff_get_color_opt(o, DIFF_CONTEXT_DIM);
 		}
-		emit_line_ws_markup(o, set_sign, set, reset, "-", line, len,
+		first = o->output_indicators[OI_OLD] ?
+			o->output_indicators[OI_OLD] : "-";
+		emit_line_ws_markup(o, set_sign, set, reset, first, line, len,
 				    flags & DIFF_SYMBOL_CONTENT_WS_MASK, 0);
 		break;
 	case DIFF_SYMBOL_WORDS_PORCELAIN:

@@ -4876,6 +4883,12 @@ int diff_opt_parse(struct diff_options *options,
 		 options->output_format |= DIFF_FORMAT_DIFFSTAT;
 	} else if (!strcmp(arg, "--no-compact-summary"))
 		 options->flags.stat_with_summary = 0;
+	else if (skip_prefix(arg, "--output-indicator-new=", &arg))
+		options->output_indicators[OI_NEW] = arg;
+	else if (skip_prefix(arg, "--output-indicator-old=", &arg))
+		options->output_indicators[OI_OLD] = arg;
+	else if (skip_prefix(arg, "--output-indicator-context=", &arg))
+		options->output_indicators[OI_CONTEXT] = arg;
 
 	/* renames options */
 	else if (starts_with(arg, "-B") ||

diff --git a/diff.h b/diff.h
index e1e54256c18..2d4097df1c7 100644
--- a/diff.h
+++ b/diff.h

@@ -194,6 +194,11 @@ struct diff_options {
 	FILE *file;
 	int close_file;
 
+#define OI_NEW 0
+#define OI_OLD 1
+#define OI_CONTEXT 2