Move pages under tldr, lint run.sh, update docs

tldr/git-symbolic-ref

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# git symbolic-ref
+
+> Read, change, or delete files that store references.
+> More information: <https://git-scm.com/docs/git-symbolic-ref>.
+
+- Store a reference by a name:
+
+`git symbolic-ref refs/{{name}} {{ref}}`
+
+- Store a reference by name, including a message with a reason for the update:
+
+`git symbolic-ref -m "{{message}}" refs/{{name}} refs/heads/{{branch_name}}`
+
+- Read a reference by name:
+
+`git symbolic-ref refs/{{name}}`
+
+- Delete a reference by name:
+
+`git symbolic-ref --delete refs/{{name}}`
+
+- For scripting, hide errors with `--quiet` and use `--short` to simplify ("refs/heads/X" prints as "X"):
+
+`git symbolic-ref --quiet --short refs/{{name}}`