diff: Help "less" hide ^M from the output

When the tracked contents have CRLF line endings, colored diff output
shows "^M" at the end of output lines, which is distracting, even though
the pager we use by default ("less") knows to hide them.

The problem is that "less" hides a carriage-return only at the end of the
line, immediately before a line feed.  The colored diff output does not
take this into account, and emits four element sequence for each line:

   - force this color;
   - the line up to but not including the terminating line feed;
   - reset color
   - line feed.

By including the carriage return at the end of the line in the second
item, we are breaking the smart our pager has in order not to show "^M".
This can be fixed by changing the sequence to:

   - force this color;
   - the line up to but not including the terminating end-of-line;
   - reset color
   - end-of-line.

where end-of-line is either a single linefeed or a CRLF pair.  When the
output is not colored, "force this color" and "reset color" sequences are
both empty, so we won't have this problem with or without this patch.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/combine-diff.c b/combine-diff.c
index 4dfc330..aa9d79e 100644 (file)
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -500,6 +500,18 @@ static int hunk_comment_line(const char *bol)
        return (isalpha(ch) || ch == '_' || ch == '$');
 }
 
+static void show_line_to_eol(const char *line, int len, const char *reset)
+{
+       int saw_cr_at_eol = 0;
+       if (len < 0)
+               len = strlen(line);
+       saw_cr_at_eol = (len && line[len-1] == '\r');
+
+       printf("%.*s%s%s\n", len - saw_cr_at_eol, line,
+              reset,
+              saw_cr_at_eol ? "\r" : "");
+}
+
 static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent,
                       int use_color)
 {
@@ -593,7 +605,7 @@ static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent,
                                        else
                                                putchar(' ');
                                }
-                               printf("%s%s\n", ll->line, c_reset);
+                               show_line_to_eol(ll->line, -1, c_reset);
                                ll = ll->next;
                        }
                        if (cnt < lno)
@@ -617,7 +629,7 @@ static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent,
                                        putchar(' ');
                                p_mask <<= 1;
                        }
-                       printf("%.*s%s\n", sl->len, sl->bol, c_reset);
+                       show_line_to_eol(sl->bol, sl->len, c_reset);
                }
        }
 }

diff --git a/diff.c b/diff.c
index 7b4300a..6d56c69 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -511,13 +511,20 @@ const char *diff_get_color(int diff_use_color, enum color_diff ix)
 
 static void emit_line(FILE *file, const char *set, const char *reset, const char *line, int len)
 {
-       int has_trailing_newline = (len > 0 && line[len-1] == '\n');
+       int has_trailing_newline, has_trailing_carriage_return;
+
+       has_trailing_newline = (len > 0 && line[len-1] == '\n');
        if (has_trailing_newline)
                len--;
+       has_trailing_carriage_return = (len > 0 && line[len-1] == '\r');
+       if (has_trailing_carriage_return)
+               len--;
 
        fputs(set, file);
        fwrite(line, len, 1, file);
        fputs(reset, file);
+       if (has_trailing_carriage_return)
+               fputc('\r', file);
        if (has_trailing_newline)
                fputc('\n', file);
 }

diff --git a/t/t4019-diff-wserror.sh b/t/t4019-diff-wserror.sh
index 7eae1f4..84a1fe3 100755 (executable)
--- a/t/t4019-diff-wserror.sh
+++ b/t/t4019-diff-wserror.sh
@@ -178,4 +178,16 @@ test_expect_success 'trailing empty lines (2)' '
 
 '
 
+test_expect_success 'do not color trailing cr in context' '
+       git config --unset core.whitespace
+       rm -f .gitattributes &&
+       echo AAAQ | tr Q "\015" >G &&
+       git add G &&
+       echo BBBQ | tr Q "\015" >>G
+       git diff --color G | tr "\015" Q >output &&
+       grep "BBB.*${blue_grep}Q" output &&
+       grep "AAA.*\[mQ" output
+
+'
+
 test_done