Every Git user will have probably been asked to set up their Git at the first time:

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git config --global user.name "Ramsay Leung"
git config --global user.email ramsayleung@gmail.com

The above command will simply add the user.name and user.email value into your ~/.gitconfig file

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> cat ~/.gitconfig
[user]
    name = Ramsay Leung
    email = ramsayleung@gmail.com
[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.

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?

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.

Fortunately, starting from Git version 2.13, Git supports conditional configuration includes, you are capable of setting up different configs for different repositories.

If you add the following config to your global config file:

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[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/.

Caution: If you forget to specify the “/” at the end of the git dir, e.g. “~/projects/oss”, Conditional Config won’t work!

Therefore, you could have a “work” directory and work-specific config here and an “oss” directory with values for your open source projects, etc.

Git also supports other filters more than gitdir, you could specify a branch name as an include filter with onbranch

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  ; 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 for more details