Update cheatsheets

tldr/yadm-enter

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# yadm-enter
+
+> Run a sub-shell with all Git variables set. This sub-shell can be used to easily interact with the local `yadm` repository using Git commands.
+> This could be useful if you are using a tool which uses Git directly.
+> More information: <https://github.com/TheLocehiliosan/yadm/blob/master/yadm.md#commands>.
+
+- Run a sub-shell with all Git variables set:
+
+`yadm enter`
+
+- Exit the sub-shell:
+
+`exit`