A new option --ignore-cr-at-eol tells the diff machinery to treat a
carriage-return at the end of a (complete) line as if it does not
exist.

This would make it easier to review a change whose only effect is to
turn line endings from CRLF to LF or the other way around.

Signed-off-by: Junio C Hamano <gits...@pobox.com>
---
 Documentation/diff-options.txt     |  3 +++
 Documentation/merge-strategies.txt |  5 +++--
 diff.c                             |  2 ++
 merge-recursive.c                  |  2 ++
 t/t4015-diff-whitespace.sh         | 28 ++++++++++++++++++++++++++++
 xdiff/xdiff.h                      |  4 +++-
 xdiff/xutils.c                     | 38 ++++++++++++++++++++++++++++++++++++--
 7 files changed, 77 insertions(+), 5 deletions(-)

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 89cc0f48de..aa2c0ff74d 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -519,6 +519,9 @@ endif::git-format-patch[]
 --text::
        Treat all files as text.
 
+--ignore-cr-at-eol::
+       Ignore carrige-return at the end of line when doing a comparison.
+
 --ignore-space-at-eol::
        Ignore changes in whitespace at EOL.
 
diff --git a/Documentation/merge-strategies.txt 
b/Documentation/merge-strategies.txt
index 2eb92b9327..030744910e 100644
--- a/Documentation/merge-strategies.txt
+++ b/Documentation/merge-strategies.txt
@@ -57,11 +57,12 @@ diff-algorithm=[patience|minimal|histogram|myers];;
 ignore-space-change;;
 ignore-all-space;;
 ignore-space-at-eol;;
+ignore-cr-at-eol;;
        Treats lines with the indicated type of whitespace change as
        unchanged for the sake of a three-way merge.  Whitespace
        changes mixed with other changes to a line are not ignored.
-       See also linkgit:git-diff[1] `-b`, `-w`, and
-       `--ignore-space-at-eol`.
+       See also linkgit:git-diff[1] `-b`, `-w`,
+       `--ignore-space-at-eol`, and `--ignore-cr-at-eol`.
 +
 * If 'their' version only introduces whitespace changes to a line,
   'our' version is used;
diff --git a/diff.c b/diff.c
index 790250fe86..dd14e4190c 100644
--- a/diff.c
+++ b/diff.c
@@ -3888,6 +3888,8 @@ int diff_opt_parse(struct diff_options *options,
                DIFF_XDL_SET(options, IGNORE_WHITESPACE_CHANGE);
        else if (!strcmp(arg, "--ignore-space-at-eol"))
                DIFF_XDL_SET(options, IGNORE_WHITESPACE_AT_EOL);
+       else if (!strcmp(arg, "--ignore-cr-at-eol"))
+               DIFF_XDL_SET(options, IGNORE_CR_AT_EOL);
        else if (!strcmp(arg, "--ignore-blank-lines"))
                DIFF_XDL_SET(options, IGNORE_BLANK_LINES);
        else if (!strcmp(arg, "--indent-heuristic"))
diff --git a/merge-recursive.c b/merge-recursive.c
index 7a7d55aabe..006b94baf2 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -2214,6 +2214,8 @@ int parse_merge_opt(struct merge_options *o, const char 
*s)
                DIFF_XDL_SET(o, IGNORE_WHITESPACE);
        else if (!strcmp(s, "ignore-space-at-eol"))
                DIFF_XDL_SET(o, IGNORE_WHITESPACE_AT_EOL);
+       else if (!strcmp(s, "ignore-cr-at-eol"))
+               DIFF_XDL_SET(o, IGNORE_CR_AT_EOL);
        else if (!strcmp(s, "renormalize"))
                o->renormalize = 1;
        else if (!strcmp(s, "no-renormalize"))
diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 289806d0c7..32dd54c21d 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -106,6 +106,8 @@ test_expect_success 'another test, without options' '
        git diff -w -b --ignore-space-at-eol >out &&
        test_cmp expect out &&
 
+       git diff -w --ignore-cr-at-eol >out &&
+       test_cmp expect out &&
 
        tr "Q_" "\015 " <<-\EOF >expect &&
        diff --git a/x b/x
@@ -128,6 +130,9 @@ test_expect_success 'another test, without options' '
        git diff -b --ignore-space-at-eol >out &&
        test_cmp expect out &&
 
+       git diff -b --ignore-cr-at-eol >out &&
+       test_cmp expect out &&
+
        tr "Q_" "\015 " <<-\EOF >expect &&
        diff --git a/x b/x
        index d99af23..22d9f73 100644
@@ -145,6 +150,29 @@ test_expect_success 'another test, without options' '
         CR at end
        EOF
        git diff --ignore-space-at-eol >out &&
+       test_cmp expect out &&
+
+       git diff --ignore-space-at-eol --ignore-cr-at-eol >out &&
+       test_cmp expect out &&
+
+       tr "Q_" "\015 " <<-\EOF >expect &&
+       diff --git a/x b/x
+       index_d99af23..22d9f73 100644
+       --- a/x
+       +++ b/x
+       @@ -1,6 +1,6 @@
+       -whitespace at beginning
+       -whitespace change
+       -whitespace in the middle
+       -whitespace at end
+       +_      whitespace at beginning
+       +whitespace_    _change
+       +white space in the middle
+       +whitespace at end__
+        unchanged line
+        CR at end
+       EOF
+       git diff --ignore-cr-at-eol >out &&
        test_cmp expect out
 '
 
diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index cbf5d8e166..51f8926215 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -33,9 +33,11 @@ extern "C" {
 #define XDF_IGNORE_WHITESPACE (1 << 1)
 #define XDF_IGNORE_WHITESPACE_CHANGE (1 << 2)
 #define XDF_IGNORE_WHITESPACE_AT_EOL (1 << 3)
+#define XDF_IGNORE_CR_AT_EOL (1 << 4)
 #define XDF_WHITESPACE_FLAGS (XDF_IGNORE_WHITESPACE | \
                              XDF_IGNORE_WHITESPACE_CHANGE | \
-                             XDF_IGNORE_WHITESPACE_AT_EOL)
+                             XDF_IGNORE_WHITESPACE_AT_EOL | \
+                             XDF_IGNORE_CR_AT_EOL)
 
 #define XDF_IGNORE_BLANK_LINES (1 << 7)
 
diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index 04d7b32e4e..b2cbcc818f 100644
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c
@@ -156,6 +156,24 @@ int xdl_blankline(const char *line, long size, long flags)
        return (i == size);
 }
 
+/*
+ * Have we eaten everything on the line, except for an optional
+ * CR at the very end?
+ */
+static int ends_with_optional_cr(const char *l, long s, long i)
+{
+       int complete = s && l[s-1] == '\n';
+
+       if (complete)
+               s--;
+       if (s == i)
+               return 1;
+       /* do not ignore CR at the end of an incomplete line */
+       if (complete && s == i + 1 && l[i] == '\r')
+               return 1;
+       return 0;
+}
+
 int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
 {
        int i1, i2;
@@ -170,7 +188,8 @@ int xdl_recmatch(const char *l1, long s1, const char *l2, 
long s2, long flags)
 
        /*
         * -w matches everything that matches with -b, and -b in turn
-        * matches everything that matches with --ignore-space-at-eol.
+        * matches everything that matches with --ignore-space-at-eol,
+        * which in turn matches everything that matches with 
--ignore-cr-at-eol.
         *
         * Each flavor of ignoring needs different logic to skip whitespaces
         * while we have both sides to compare.
@@ -204,6 +223,14 @@ int xdl_recmatch(const char *l1, long s1, const char *l2, 
long s2, long flags)
                        i1++;
                        i2++;
                }
+       } else if (flags & XDF_IGNORE_CR_AT_EOL) {
+               /* Find the first difference and see how the line ends */
+               while (i1 < s1 && i2 < s2 && l1[i1] == l2[i2]) {
+                       i1++;
+                       i2++;
+               }
+               return (ends_with_optional_cr(l1, s1, i1) &&
+                       ends_with_optional_cr(l2, s2, i2));
        }
 
        /*
@@ -230,9 +257,16 @@ static unsigned long xdl_hash_record_with_whitespace(char 
const **data,
                char const *top, long flags) {
        unsigned long ha = 5381;
        char const *ptr = *data;
+       int cr_at_eol_only = (flags & XDF_WHITESPACE_FLAGS) == 
XDF_IGNORE_CR_AT_EOL;
 
        for (; ptr < top && *ptr != '\n'; ptr++) {
-               if (XDL_ISSPACE(*ptr)) {
+               if (cr_at_eol_only) {
+                       /* do not ignore CR at the end of an incomplete line */
+                       if (*ptr == '\r' &&
+                           (ptr + 1 < top && ptr[1] == '\n'))
+                               continue;
+               }
+               else if (XDL_ISSPACE(*ptr)) {
                        const char *ptr2 = ptr;
                        int at_eol;
                        while (ptr + 1 < top && XDL_ISSPACE(ptr[1])
-- 
2.15.0-263-g47cc852023

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