Merge pull request IntersectMBO#1130 from input-output-hk/erikd/hlint…

…-hook

doc: Add hlint-stylish-haskell.md

doc/hlint-stylish-haskell.md

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+# Auto-running hlint and stylish-haskell on Commit
+
+This document describes how to have `hlint` and `stylish-haskell` locally on every commit.
+
+# Installing Them
+
+Installing these two is as simple as `cabal install hlint stylish-haskell` which will install them
+in `$HOME/.cabal/bin` which should then be added to your `PATH` environment variable.
+
+# Install the Git Pre-commit Hook
+
+In the `db-sync` repo, there is a shell script at `scripts/git-pre-commit-hook`. This can be
+symlinked to run as a Git pre-commit hook. If you go to the `.git` directory of your
+`cardano-db-sync` Git checkout and create the symlink as follows:
+```
+(cd .git/hooks/ && ln -s ../../scripts/git-pre-commit-hook pre-commit)
+```