Update cheatsheets

linux/apt-add-repository

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+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# apt-add-repository
+
+> Manages `apt` repository definitions.
+> More information: <https://manpages.debian.org/latest/software-properties-common/apt-add-repository.1.html>.
+
+- Add a new `apt` repository:
+
+`apt-add-repository {{repository_spec}}`
+
+- Remove an `apt` repository:
+
+`apt-add-repository --remove {{repository_spec}}`
+
+- Update the package cache after adding a repository:
+
+`apt-add-repository --update {{repository_spec}}`
+
+- Enable source packages:
+
+`apt-add-repository --enable-source {{repository_spec}}`