Avoid conflicts when merging branches with mixed normalization

Currently, merging across changes in line ending normalization is
painful since files containing CRLF will conflict with normalized files,
even if the only difference between the two versions is the line
endings.  Additionally, any "real" merge conflicts that exist are
obscured because every line in the file has a conflict.

Assume you start out with a repo that has a lot of text files with CRLF
checked in (A):

      o---C
     /     \
    A---B---D

B: Add "* text=auto" to .gitattributes and normalize all files to
   LF-only

C: Modify some of the text files

D: Try to merge C

You will get a ridiculous number of LF/CRLF conflicts when trying to
merge C into D, since the repository contents for C are "wrong" wrt the
new .gitattributes file.

Fix ll-merge so that the "base", "theirs" and "ours" stages are passed
through convert_to_worktree() and convert_to_git() before a three-way
merge.  This ensures that all three stages are normalized in the same
way, removing from consideration differences that are only due to
normalization.

This feature is optional for now since it changes a low-level mechanism
and is not necessary for the majority of users.  The "merge.renormalize"
config variable enables it.

Signed-off-by: Eyvind Bernhardsen <eyvind.bernhardsen@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/t/t6038-merge-text-auto.sh b/t/t6038-merge-text-auto.sh
new file mode 100755
index 0000000..127baf8
--- /dev/null
+++ b/t/t6038-merge-text-auto.sh
@@ -0,0 +1,64 @@
+#!/bin/sh
+
+test_description='CRLF merge conflict across text=auto change'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	git config merge.renormalize true &&
+	git config core.autocrlf false &&
+	echo first line | append_cr >file &&
+	echo first line >control_file &&
+	echo only line >inert_file &&
+	git add file control_file inert_file &&
+	git commit -m "Initial" &&
+	git tag initial &&
+	git branch side &&
+	echo "* text=auto" >.gitattributes &&
+	touch file &&
+	git add .gitattributes file &&
+	git commit -m "normalize file" &&
+	echo same line | append_cr >>file &&
+	echo same line >>control_file &&
+	git add file control_file &&
+	git commit -m "add line from a" &&
+	git tag a &&
+	git rm .gitattributes &&
+	rm file &&
+	git checkout file &&
+	git commit -m "remove .gitattributes" &&
+	git tag c &&
+	git checkout side &&
+	echo same line | append_cr >>file &&
+	echo same line >>control_file &&
+	git add file control_file &&
+	git commit -m "add line from b" &&
+	git tag b &&
+	git checkout master
+'
+
+test_expect_success 'Check merging after setting text=auto' '
+	git reset --hard a &&
+	git merge b &&
+	cat file | remove_cr >file.temp &&
+	test_cmp file file.temp
+'
+
+test_expect_success 'Check merging addition of text=auto' '
+	git reset --hard b &&
+	git merge a &&
+	cat file | remove_cr >file.temp &&
+	test_cmp file file.temp
+'
+
+test_expect_failure 'Test delete/normalize conflict' '
+	git checkout side &&
+	git reset --hard initial &&
+	git rm file &&
+	git commit -m "remove file" &&
+	git checkout master &&
+	git reset --hard a^ &&
+	git merge side
+'
+
+test_done