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2019-04-08merge-recursive: switch directory rename detection defaultLibravatar Elijah Newren1-4/+4
When all of x/a, x/b, and x/c have moved to z/a, z/b, and z/c on one branch, there is a question about whether x/d added on a different branch should remain at x/d or appear at z/d when the two branches are merged. There are different possible viewpoints here: A) The file was placed at x/d; it's unrelated to the other files in x/ so it doesn't matter that all the files from x/ moved to z/ on one branch; x/d should still remain at x/d. B) x/d is related to the other files in x/, and x/ was renamed to z/; therefore x/d should be moved to z/d. Since there was no ability to detect directory renames prior to git-2.18, users experienced (A) regardless of context. Choice (B) was implemented in git-2.18, with no option to go back to (A), and has been in use since. However, one user reported that the merge results did not match their expectations, making the change of default problematic, especially since there was no notice printed when directory rename detection moved files. Note that there is also a third possibility here: C) There are different answers depending on the context and content that cannot be determined by git, so this is a conflict. Use a higher stage in the index to record the conflict and notify the user of the potential issue instead of silently selecting a resolution for them. Add an option for users to specify their preference for whether to use directory rename detection, and default to (C). Even when directory rename detection is on, add notice messages about files moved into new directories. As a sidenote, x/d did not have to be a new file here; it could have already existed at some other path and been renamed to x/d, with directory rename detection just renaming it again to z/d. Thus, it's not just new files, but also a modification to all rename types (normal renames, rename/add, rename/delete, rename/rename(1to1), rename/rename(1to2), and rename/rename(2to1)). Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-08-30am: avoid directory rename detection when calling recursive merge machineryLibravatar Elijah Newren1-2/+2
Let's say you have the following three trees, where Base is from one commit behind either master or branch: Base : bar_v1, foo/{file1, file2, file3} branch: bar_v2, foo/{file1, file2}, goo/file3 master: bar_v3, foo/{file1, file2, file3} Using git-am (or am-based rebase) to apply the changes from branch onto master results in the following tree: Result: bar_merged, goo/{file1, file2, file3} This is not what users want; they did not rename foo/ -> goo/, they only renamed one file within that directory. The reason this happens is am constructs fake trees (via build_fake_ancestor()) of the following form: Base_bfa : bar_v1, foo/file3 branch_bfa: bar_v2, goo/file3 Combining these two trees with master's tree: master: bar_v3, foo/{file1, file2, file3}, You can see that merge_recursive_generic() would see branch_bfa as renaming foo/ -> goo/, and master as just adding both foo/file1 and foo/file2. As such, it ends up with goo/{file1, file2, file3} The core problem is that am does not have access to the original trees; it can only construct trees using the blobs involved in the patch. As such, it is not safe to perform directory rename detection within am -3. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-08-30t3401: add another directory rename testcase for rebase and amLibravatar Elijah Newren1-1/+109
Similar to commit 16346883ab ("t3401: add directory rename testcases for rebase and am", 2018-06-27), add another testcase for directory rename detection. This new testcase differs in that it showcases a situation where no directory rename was performed, but which some backends incorrectly detect. As with the other testcase, run this in conjunction with each of the types of rebases: git-rebase--interactive git-rebase--am git-rebase--merge and also use the same testcase for git am --3way Reported-by: Nikolay Kasyanov <corrmage@gmail.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-06-27t3401: add directory rename testcases for rebase and amLibravatar Elijah Newren1-0/+105
Add a simple directory rename testcase, in conjunction with each of the types of rebases: git-rebase--interactive git-rebase--am git-rebase--merge and also use the same testcase for git am --3way This demonstrates a difference in behavior between the different rebase backends in regards to directory rename detection. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>