diff: do not short-cut CHECK_SIZE_ONLY check in diff_populate_filespec()

Callers of diff_populate_filespec() can choose to ask only for the
size of the blob without grabbing the blob data, and the function,
after running lstat() when the filespec points at a working tree
file, returns by copying the value in size field of the stat
structure into the size field of the filespec when this is the case.

However, this short-cut cannot be taken if the contents from the
path needs to go through convert_to_git(), whose resulting real blob
data may be different from what is in the working tree file.

As "git diff --quiet" compares the .size fields of filespec
structures to skip content comparison, this bug manifests as a
false "there are differences" for a file that needs eol conversion,
for example.

Reported-by: Mike Crowe <mac@mcrowe.com>
Helped-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/diff.c b/diff.c
index 059123c5dcef4129763895b0f2ad5a54728b0c07..37e60ca601fe4c3c106fe7dbdbf3d7fe05adfcf1 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -2783,8 +2783,25 @@ int diff_populate_filespec(struct diff_filespec *s, unsigned int flags)
                        s->should_free = 1;
                        return 0;
                }
-               if (size_only)
+
+               /*
+                * Even if the caller would be happy with getting
+                * only the size, we cannot return early at this
+                * point if the path requires us to run the content
+                * conversion.
+                */
+               if (size_only && !would_convert_to_git(s->path))
                        return 0;
+
+               /*
+                * Note: this check uses xsize_t(st.st_size) that may
+                * not be the true size of the blob after it goes
+                * through convert_to_git().  This may not strictly be
+                * correct, but the whole point of big_file_threshold
+                * and is_binary check being that we want to avoid
+                * opening the file and inspecting the contents, this
+                * is probably fine.
+                */
                if ((flags & CHECK_BINARY) &&
                    s->size > big_file_threshold && s->is_binary == -1) {
                        s->is_binary = 1;

diff --git a/t/t4035-diff-quiet.sh b/t/t4035-diff-quiet.sh
index 461f4bb583d081c58c8ab55bf4cedae8a361cd43..2f1737fcef185486dc626d616c37fdadc11deba1 100755 (executable)
--- a/t/t4035-diff-quiet.sh
+++ b/t/t4035-diff-quiet.sh
@@ -152,4 +152,13 @@ test_expect_success 'git diff --quiet ignores stat-change only entries' '
        test_expect_code 1 git diff --quiet
 '
 
+test_expect_success 'git diff --quiet on a path that need conversion' '
+       echo "crlf.txt text=auto" >.gitattributes &&
+       printf "Hello\r\nWorld\r\n" >crlf.txt &&
+       git add .gitattributes crlf.txt &&
+
+       printf "Hello\r\nWorld\n" >crlf.txt &&
+       git diff --quiet crlf.txt
+'
+
 test_done