A Comprehensive Guide to Git Format-Patch Command

Git is a distributed version control system that allows developers to collaborate on a project effectively. Git format-patch is a command that helps developers create patches from their Git commits. This command is quite useful for various reasons, such as code reviews, sharing code changes between branches, and submitting patches to mailing lists. In this article, we will provide a detailed explanation of the git format-patch command and how to use it effectively.

Understanding Git Format-Patch Command

Git format-patch command is a Git command that helps create formatted patches from Git commits. A patch is a file that contains the differences between a file’s content and the changes made to it. Developers use patches to share changes between Git repositories or to submit code changes for review.

The git format-patch command creates patches from one or more Git commits. These patches can be used with the git apply command to apply changes to another Git repository. The format-patch command creates patches in the Git mailbox format by default. However, it can also output patches in other formats such as raw, mbox, and inlined email.

Using Git Format-Patch Command

The git format-patch command can be used in two ways: by specifying a range of commits, or by specifying one or more commits individually.

Using Git Format-Patch with Commit Range

The following command generates patches for all the commits in the range between \<start-commit> and \<end-commit>:

$ git format-patch \<start-commit\>..\<end-commit\>

For example, to generate patches for the last two commits, you can use the following Git command:

$ git format-patch HEAD~2..HEAD

Using Git Format-Patch with Individual Commits

You can also generate patches for individual commits by specifying them in the Git command. For example, to generate a patch for a specific commit, you can use the following command:

$ git format-patch -1 \<commit-SHA\>

The -1 option specifies that only one patch should be generated. The \<commit-SHA> is the Git commit hash of the commit you want to generate a patch for.

Output Format Options

The git format-patch command can output patches in various formats. By default, it outputs patches in the Git mailbox format. However, you can use the following options to output patches in other formats:

• --stdout option outputs the patch on standard output instead of writing it to a file. This option is useful when you want to pipe patches to other Git commands or tools.
• --mbox option outputs patches in mbox format. This format is useful when sending patches via email.
• --raw option outputs patches in raw format. This format is useful when you want to apply patches to non-Git repositories.
• --numbered option numbers patches sequentially. This option is useful when you want to generate multiple patches and keep them in a specific order.

Here is an example of how to use the git format-patch command with the --mbox option:

$ git format-patch --mbox -1 \<commit-SHA\> 

This command generates a patch in mbox format for the specified Git commit.

Applying Git Patches

Git patches generated using git format-patch can be applied using the git apply command. The git apply command applies patches to the codebase by modifying existing files or creating new ones.

To apply a patch generated using git format-patch, simply use the following command:

$ git apply \<patch-file\>

For example, to apply a patch named "change.patch," you can use the following Git command:

$ git apply change.patch

The git apply command can also be used with various options such as --check to check if a patch can be applied cleanly, --reject to create a patch file with rejected changes, and --index to add the changes to the Git index.

Conclusion

Git format-patch command is a useful command for creating patches from Git commits. These patches can be used to share code changes between repositories or submit them for review. You can use the git format-patch command with a range of commits or individual commits to generate patches in various formats. The git apply command can be used to apply these patches to another repository or codebase. We hope this guide has provided you with a comprehensive explanation of the Git format-patch command and how to use it.