Whenever dealing with the Git merge operations, conflicts will be the frequently occurred. When more than two developers work on the same file on different systems using Git, they encounter more merge conflicts than usual. Sometimes Git itself helps its users to solve this problem by automatically suggesting how to handle the conflict. Usually, conflicts occur when working on the same file two people change the same code snippet, leaving Git ambiguous about which change should be implemented. Merge conflicts could also arise when one of the developers is modifying a file which is already deleted by the other user. In such cases, Git cannot find the solution to this problem automatically, so then Git would notify the developer performing the merge that a conflict has occurred and terminate the operation. Only the developer performing the merge would know about the conflict, and now it would be the user's responsibility to resolve this conflict.
Classification of merge conflicts
Based on the time of occurrence of the conflict, Merge conflicts are classified into two groups:
1. While starting the merge
Some of the conflicts arise when the merge has just been started; this occurs when Git witness that the user made some changes in the directory the developer is currently working in or the staging area is not up to date. In such cases, Git doesn't even try to start the merge as the changes that were remaining would be overwritten by the commits the developer is trying to Merge; this type of conflict does not arise due to the other developer's code but because of the pending disputes with local changes. To resolve such merge conflict, you need to stabilize the local state before the merge operation using the GIT commands like Git checkout, Git commit or Git reset.
2. Conflicts during the merge
This type of conflict occurs when the merge is halfway and encounters any code snippet or any particular code line that would cause the condition of ambiguity in the program. Git tries its best to resolve the conflicts on its own and merge the local branch with the specified target branch. If not automatically resolved, the conflict is then notified to the developer to resolve the issue. When a halfway conflict occurs, Git would print out the error message like "<filename> would be overwritten by merge cannot merge."
The easier way to recognize the condition of merge conflicts
As you have seen that in any case of a merge conflict, Git returns an error message with the text "merge failed" in it, but this doesn't help the user to identify the problem properly and to gain some more insights into the conflict you can use the Git status command which outputs a line printed on the console that indicates the presence of some parts that are still not merged in the final file that was being merged. The current file would now be modified by Git, to let you know the area of conflicts, and on examining the file by using a separate editor or the cat command, you would encounter some strange additions in your file that were modified by Git
- <<<<<<<HEAD// the first line
- ======= // the center (midpoint) of conflict code
- >>>>>>>new_branch_to_merge_later // the end
These new lines can be thought of as the conflict separators or the conflict divider that help you understand the things you need to change to handle the conflicts. The first line marks the start of your conflict region. The code lines after the headline and before the central line are the part of code that is in the current branch, and similarly, the code snippet between the central line and the end line is code that causes the conflict and is present in the branch to be merged in.
Ways to resolve any Merge-conflict
The easiest and the most common way to solve any merge conflict is to directly edit the current file being merged and resolve all the disputes. You can change each code that causes any conflict and then merge the file and finalize the merge you have now executed using the commit command.
Some common get command-line tools you can use for handling merge conflicts
However, merge conflicts are hard to understand and resolve, but you are lucky as Git provides you with many useful command-line tools that are discussed now that can help you overcome such problems:
- Git status: Identify the conflicted files easily using this command
- Git log --merge: Returns the list of commits that cause the conflict.
- Git diff: Gives the difference b/w the two files
- Git checkout: Used usually to stabilize local states
- Git reset: Used to reset the files that were being merged
- Git merge --abort: Aborts the merge operation.