Configuration File Management on GitHub

dotnet, configuration, github comments edit

I hate configuration files! They contain highly sensitive information and there is always a risk of them leaking out. Especially when I read horror stories like this I remind myself to be more careful about it. It is particularly important when starting off with a private repository and converting it to open-source.

There are a few approaches and I will try to make pros and cons list for each of them which hopefully would make it easier for me to make a decision.

Method 1: Ignore config files completely

Simply add to gitignore before checking in the config files. This is not really a viable option but to cover all basis I wanted to add this one as well.

Pros

  • Very easy to implement
  • Easy to be consistent (use the same gitignore everywhere)

Cons

  • When someone checks out the project initially it wouldn’t compile because of the missing config file.
  • For a new user there is no way to figure out what the actual config should look like
  • For internal applications, you have to maintain local copies and handle distribution among developers manually.

Method 2: Check in configuration with placeholders

Check in the initial file then run the following command:

git update-index --assume-unchanged <file>

After this you can add the actual values and use the config as usual. But those values will be ignored. This way when someone checks out they can at least compile the project.

Pros

  • Less disruptive as the project can be compiled

Cons

  • When you make a change to the config file (e.g. add/rename keys) you can’t check in those changes as well

Method 3: Ignore config file, check in a sample file instead

This is essentially a merger of Method 1 and 2. Maintain two files (e.g. App.config and App.config.sample). Ignore the app.config from the getgo and only check in .sample file. Structurally it will be exactly the same as app.config without the confidential values.

Pros

  • Won’t compile by default, extra step for the people who check out (small one but still)

Cons

  • Both files need to be kept in sync manually
  • Still no online copy of the actual config file available

Method 4: Reference to another configuration file

A slight variation of the previous method. .NET allows cascading and linking with configuration files. For example say this is my app.config file:

<configuration>
	<appSettings file="Actual.config">
		<add key="Twilio.AccountSID" value="SAMPLE SID" />
		<add key="Twilio.AuthToken" value="SAMPLE TOKEN" />
		<add key="Non-sensitive-info" value="some value" />
	</appSettings>
</configuration>

I can link the appSettings section to another file named actual.config which would look like this:

<appSettings>
  <add key="Twilio.AccountSID" value="REAL 123456" />
  <add key="Twilio.AuthToken" value="REAL Token" />
  <add key="Non-sensitive-info" value="some value" />
</appSettings>

Actual.config never goes into source control. When the application cannot find the actual.config it just uses the values in the app.config. When the actual.config is present, those values override the sample values.

Pros

  • Only keys with sensitive values can be hidden

Cons

  • Doesn’t work with custom config sections
  • Still no online copy of the actual config file available

The idea is to maintain a private repository that contains the config files and add it as a submodule:

git submodule add git@github.com:volkanx/private-config.git

And link to that configuration file in the app.config as in Method 4.

Pros

  • Actual values are online and accessible

Cons

  • Requires a paid account for private repositories
  • More complicated

Verdict

As I already have a paid GitHub account the con for Method 5 is not quite valid for me so I think I will go with that one. Otherwise the actual values will be stored locally on the disk only and will eventually get lost. Looks like there is no convenient and easy way of doing it after all. If you have any suggestions I’m all ears.

As I said, I hate configuration files!

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