Add TIL: git conditional configs.

Author: ramsayleung

content/en/post/2024/git_conditional_configs.md

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+title = "TIL: Git Conditional Configs"
+date = 2024-04-07T12:38:00-07:00
+lastmod = 2024-04-07T14:23:13-07:00
+tags = ["til", "git"]
+categories = ["til", "git"]
+draft = false
+toc = true
++++
+
+Every Git user will have probably been asked to set up their Git at the first time: <br/>
+
+```sh
+git config --global user.name "Ramsay Leung"
+git config --global user.email [email protected]
+```
+
+The above command will simply add the `user.name` and `user.email` value into your `~/.gitconfig` file <br/>
+
+```sh
+> cat ~/.gitconfig
+[user]
+    name = Ramsay Leung
+    email = [email protected]
+[core]
+    quotepath = false
+[init]
+    defaultBranch = master
+```
+
+You could also specify `--local` argument to writes the config values to `.git/config` in whatever project you're currently in. <br/>
+
+If you need to simultaneously contribute to your work and open source project on the same laptop, with different Git config values, e.g.(company email address for work-specific projects, personal email address for open source project), what should you do? <br/>
+
+You could definitely set up work-specific config as global config, then set up personal config with `--local` for every personal project separately. It works, but tedious and easy to mess-up. <br/>
+
+Fortunately, starting from Git version 2.13, Git supports conditional configuration includes, you are capable of setting up different configs for different repositories. <br/>
+
+If you add the following config to your global config file: <br/>
+
+```toml
+[includeIf "gitdir:~/projects/oss/"]
+    path = ~/.gitconfig-oss
+
+[includeIf "gitdir:~/projects/work/"]
+    path = ~/.gitconfig-work
+```
+
+Then Git will look in the `~/.gitconfig-oss` files for values only if the project you are currently working on matches `~/projects/oss/`. <br/>
+
+****Caution****: If you forget to specify the "/" at the end of the git dir, e.g. "~/projects/oss", Conditional Config won't work! <br/>
+
+Therefore, you could have a "work" directory and work-specific config here and an "oss" directory with values for your open source projects, etc. <br/>
+
+{{< figure src="/ox-hugo/conditional_config.png" >}} <br/>
+
+Git also supports other filters more than `gitdir`, you could specify a branch name as an include filter with `onbranch` <br/>
+
+```toml
+  ; include only if we are in a worktree where foo-branch is
+; currently checked out
+[includeIf "onbranch:foo-branch"]
+        path = foo.inc
+```
+
+Check out [the Git docs](https://git-scm.com/docs/git-config?ref=blog.gitbutler.com#_includes) for more details <br/>
+