add boolean diff.suppress-blank-empty config option

GNU diff's --suppress-blank-empty option makes it so that diff no
longer outputs trailing white space unless the input data has it.
With this option, empty context lines are now empty also in diff -u output.
Before, they would have a single trailing space.

 * diff.c (diff_suppress_blank_empty): New global.
   (git_diff_basic_config): Set it.
   (fn_out_consume): Honor it.
 * t/t4029-diff-trailing-space.sh: New file.
 * Documentation/config.txt: Document it.

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 676c39bb8436f35e1471b8dd50fd888ae1ac5c6b..9020675866e6af6252b83d7df0bb8bc78249f4a6 100644 (file)
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -567,6 +567,10 @@ diff.autorefreshindex::
        affects only 'git-diff' Porcelain, and not lower level
        'diff' commands, such as 'git-diff-files'.
 
+diff.suppress-blank-empty::
+       A boolean to inhibit the standard behavior of printing a space
+       before each empty output line. Defaults to false.
+
 diff.external::
        If this config variable is set, diff generation is not
        performed using the internal diff machinery, but using the

diff --git a/diff.c b/diff.c
index bf5d5f15a3b54f1e1a0a2068990e899fd869d435..fe43407b78150fd7fffe0d1fdff3456346ea27a6 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -20,6 +20,7 @@
 
 static int diff_detect_rename_default;
 static int diff_rename_limit_default = 200;
+static int diff_suppress_blank_empty;
 int diff_use_color_default = -1;
 static const char *external_diff_cmd_cfg;
 int diff_auto_refresh_index = 1;
@@ -176,6 +177,12 @@ int git_diff_basic_config(const char *var, const char *value, void *cb)
                return 0;
        }
 
+       /* like GNU diff's --suppress-blank-empty option  */
+       if (!strcmp(var, "diff.suppress-blank-empty")) {
+               diff_suppress_blank_empty = git_config_bool(var, value);
+               return 0;
+       }
+
        if (!prefixcmp(var, "diff.")) {
                const char *ep = strrchr(var, '.');
                if (ep != var + 4) {
@@ -580,6 +587,12 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
                ecbdata->label_path[0] = ecbdata->label_path[1] = NULL;
        }
 
+       if (diff_suppress_blank_empty
+           && len == 2 && line[0] == ' ' && line[1] == '\n') {
+               line[0] = '\n';
+               len = 1;
+       }
+
        /* This is not really necessary for now because
         * this codepath only deals with two-way diffs.
         */

diff --git a/t/t4029-diff-trailing-space.sh b/t/t4029-diff-trailing-space.sh
new file mode 100755 (executable)
index 0000000..4ca65e0
--- /dev/null
+++ b/t/t4029-diff-trailing-space.sh
@@ -0,0 +1,39 @@
+#!/bin/bash
+#
+# Copyright (c) Jim Meyering
+#
+test_description='diff honors config option, diff.suppress-blank-empty'
+
+. ./test-lib.sh
+
+cat <<\EOF > exp ||
+diff --git a/f b/f
+index 5f6a263..8cb8bae 100644
+--- a/f
++++ b/f
+@@ -1,2 +1,2 @@
+
+-x
++y
+EOF
+exit 1
+
+test_expect_success \
+    "$test_description" \
+    'printf "\nx\n" > f &&
+     git add f &&
+     git commit -q -m. f &&
+     printf "\ny\n" > f &&
+     git config --bool diff.suppress-blank-empty true &&
+     git diff f > actual &&
+     test_cmp exp actual &&
+     perl -i.bak -p -e "s/^\$/ /" exp &&
+     git config --bool diff.suppress-blank-empty false &&
+     git diff f > actual &&
+     test_cmp exp actual &&
+     git config --bool --unset diff.suppress-blank-empty &&
+     git diff f > actual &&
+     test_cmp exp actual
+     '
+
+test_done