The “git am” command in Git is used to apply patch files, which can be particularly useful when receiving commits via email. It allows you to apply a series of patches to your Git repository, essentially integrating changes that were sent as patch files.
Here’s how the “git am” command works:
- Receiving Commits via Email: In some collaborative workflows, contributors may submit changes in the form of patch files via email. These patch files typically contain a series of changesets or commits that need to be applied to a Git repository.
- Applying Patch Files: To apply these patch files, you can use the “git am” command followed by the path to the patch file(s). Git will read the patch file(s), extract the changesets or commits, and apply them sequentially to the repository.
- Patch Format: Patch files typically follow the unified diff format, which represents the differences between the original files and the modified files. The patch file contains information about which lines were added, modified, or deleted in each file.
- Commit Message and Authorship: Patch files often include commit messages and authorship information for each changeset. When applying the patches with “git am,” Git will extract this information and use it to create new commits in the repository, preserving the original commit messages and authorship.
- Applying Patches in Order: The “git am” command applies patches in the order they appear in the patch file(s). If the patches depend on each other, it’s crucial to apply them in the correct order to maintain the intended changes and avoid conflicts.
- Handling Conflicts: In some cases, conflicts may arise when applying patches with “git am.” Conflicts occur when the changes in the patch files conflict with existing changes in the repository. Git will pause the patching process and provide you with options to resolve the conflicts manually.
- Patch Application Metadata: “git am” also records metadata about the applied patches, such as the subject line and the sender’s email address. This information is stored in the .git/rebase-apply directory.
- Commit IDs: Once the patches are successfully applied, Git assigns new commit IDs to the applied changesets. These new commits become part of the repository’s history.
Using the “git am” command simplifies the process of integrating changes received as patch files via email. It allows you to seamlessly apply patches, preserve commit messages and authorship information, and incorporate the changes into your Git repository. This is particularly helpful when collaborating with contributors who prefer to submit changes as patch files rather than pushing them directly to a shared repository.
git am Command Examples
1. Apply a patch file:
# git am /path/to/file.patch
2. Abort the process of applying a patch file:
# git am --abort
3. Apply as much of a patch file as possible, saving failed hunks to reject files:
# git am --reject /path/to/file.patch