8.1 Customizing Git - Git Configuration

By default, Git uses whatever you’ve set as your default text editor via one of the shell environment variables VISUAL or EDITOR, or else falls back to the vi editor to create and edit your commit and tag messages. To change that default to something else, you can use the core.editor setting:

Now, no matter what is set as your default shell editor, Git will fire up Emacs to edit messages.

If you set this to the path of a file on your system, Git will use that file as the default initial message when you commit. The value in creating a custom commit template is that you can use it to remind yourself (or others) of the proper format and style when creating a commit message.

For instance, consider a template file at ~/.gitmessage.txt that looks like this:

Note how this commit template reminds the committer to keep the subject line short (for the sake of git log --oneline output), to add further detail under that, and to refer to an issue or bug tracker ticket number if one exists.

To tell Git to use it as the default message that appears in your editor when you run git commit, set the commit.template configuration value:

Then, your editor will open to something like this for your placeholder commit message when you commit:

If your team has a commit-message policy, then putting a template for that policy on your system and configuring Git to use it by default can help increase the chance of that policy being followed regularly.

This setting determines which pager is used when Git pages output such as log and diff. You can set it to more or to your favorite pager (by default, it’s less), or you can turn it off by setting it to a blank string:

If you run that, Git will page the entire output of all commands, no matter how long they are.

If you’re making signed annotated tags (as discussed in Signing Your Work), setting your GPG signing key as a configuration setting makes things easier. Set your key ID like so:

Now, you can sign tags without having to specify your key every time with the git tag command:

You can put patterns in your project’s .gitignore file to have Git not see them as untracked files or try to stage them when you run git add on them, as discussed in Ignoring Files.

But sometimes you want to ignore certain files for all repositories that you work with. If your computer is running macOS, you’re probably familiar with .DS_Store files. If your preferred editor is Emacs or Vim, you know about filenames that end with a ~ or .swp.

This setting lets you write a kind of global .gitignore file. If you create a ~/.gitignore_global file with these contents:

…and you run git config --global core.excludesfile ~/.gitignore_global, Git will never again bother you about those files.

If you mistype a command, it shows you something like this:

Git helpfully tries to figure out what you meant, but it still refuses to do it. If you set help.autocorrect to 1, Git will actually run this command for you:

Note that “0.1 seconds” business. help.autocorrect is actually an integer which represents tenths of a second. So if you set it to 50, Git will give you 5 seconds to change your mind before executing the autocorrected command.

Git automatically colors most of its output, but there’s a master switch if you don’t like this behavior. To turn off all Git’s colored terminal output, do this:

The default setting is auto, which colors output when it’s going straight to a terminal, but omits the color-control codes when the output is redirected to a pipe or a file.

You can also set it to always to ignore the difference between terminals and pipes. You’ll rarely want this; in most scenarios, if you want color codes in your redirected output, you can instead pass a --color flag to the Git command to force it to use color codes. The default setting is almost always what you’ll want.

If you want to be more specific about which commands are colored and how, Git provides verb-specific coloring settings. Each of these can be set to true, false, or always:

In addition, each of these has subsettings you can use to set specific colors for parts of the output, if you want to override each color. For example, to set the meta information in your diff output to blue foreground, black background, and bold text, you can run

You can set the color to any of the following values: normal, black, red, green, yellow, blue, magenta, cyan, or white. If you want an attribute like bold in the previous example, you can choose from bold, dim, ul (underline), blink, and reverse (swap foreground and background).

If you’re programming on Windows and working with people who are not (or vice-versa), you’ll probably run into line-ending issues at some point. This is because Windows uses both a carriage-return character and a linefeed character for newlines in its files, whereas Mac and Linux systems use only the linefeed character. This is a subtle but incredibly annoying fact of cross-platform work; many editors on Windows silently replace existing LF-style line endings with CRLF, or insert both line-ending characters when the user hits the enter key.

Git can handle this by auto-converting CRLF line endings into LF when you add a file to the index, and vice versa when it checks out code onto your filesystem. You can turn on this functionality with the core.autocrlf setting. If you’re on a Windows machine, set it to true — this converts LF endings into CRLF when you check out code:

If you’re on a Linux or Mac system that uses LF line endings, then you don’t want Git to automatically convert them when you check out files; however, if a file with CRLF endings accidentally gets introduced, then you may want Git to fix it. You can tell Git to convert CRLF to LF on commit but not the other way around by setting core.autocrlf to input:

This setup should leave you with CRLF endings in Windows checkouts, but LF endings on Mac and Linux systems and in the repository.

If you’re a Windows programmer doing a Windows-only project, then you can turn off this functionality, recording the carriage returns in the repository by setting the config value to false:

Git comes preset to detect and fix some whitespace issues. It can look for six primary whitespace issues — three are enabled by default and can be turned off, and three are disabled by default but can be activated.

The three that are turned on by default are blank-at-eol, which looks for spaces at the end of a line; blank-at-eof, which notices blank lines at the end of a file; and space-before-tab, which looks for spaces before tabs at the beginning of a line.

The three that are disabled by default but can be turned on are indent-with-non-tab, which looks for lines that begin with spaces instead of tabs (and is controlled by the tabwidth option); tab-in-indent, which watches for tabs in the indentation portion of a line; and cr-at-eol, which tells Git that carriage returns at the end of lines are OK.

You can tell Git which of these you want enabled by setting core.whitespace to the values you want on or off, separated by commas. You can disable an option by prepending a - in front of its name, or use the default value by leaving it out of the setting string entirely. For example, if you want all but space-before-tab to be set, you can do this (with trailing-space being a short-hand to cover both blank-at-eol and blank-at-eof):

Or you can specify the customizing part only:

Git will detect these issues when you run a git diff command and try to color them so you can possibly fix them before you commit. It will also use these values to help you when you apply patches with git apply. When you’re applying patches, you can ask Git to warn you if it’s applying patches with the specified whitespace issues:

Or you can have Git try to automatically fix the issue before applying the patch:

These options apply to the git rebase command as well. If you’ve committed whitespace issues but haven’t yet pushed upstream, you can run git rebase --whitespace=fix to have Git automatically fix whitespace issues as it’s rewriting the patches.

Git is capable of making sure every object received during a push still matches its SHA-1 checksum and points to valid objects. However, it doesn’t do this by default; it’s a fairly expensive operation, and might slow down the operation, especially on large repositories or pushes. If you want Git to check object consistency on every push, you can force it to do so by setting receive.fsckObjects to true:

Now, Git will check the integrity of your repository before each push is accepted to make sure faulty (or malicious) clients aren’t introducing corrupt data.

If you rebase commits that you’ve already pushed and then try to push again, or otherwise try to push a commit to a remote branch that doesn’t contain the commit that the remote branch currently points to, you’ll be denied. This is generally good policy; but in the case of the rebase, you may determine that you know what you’re doing and can force-update the remote branch with a -f flag to your push command.

To tell Git to refuse force-pushes, set receive.denyNonFastForwards:

The other way you can do this is via server-side receive hooks, which we’ll cover in a bit. That approach lets you do more complex things like deny non-fast-forwards to a certain subset of users.

One of the workarounds to the denyNonFastForwards policy is for the user to delete the branch and then push it back up with the new reference. To avoid this, set receive.denyDeletes to true:

This denies any deletion of branches or tags — no user can do it. To remove remote branches, you must remove the ref files from the server manually. There are also more interesting ways to do this on a per-user basis via ACLs, as you’ll learn in An Example Git-Enforced Policy.