Format transcrypt with shfmt and document this step

Author: jmurty

.editorconfig

@@ -7,7 +7,7 @@ insert_final_newline = true
 trim_trailing_whitespace = true
 
 [*.md]
-indent_size = 4
+indent_size = 2
 indent_style = space
 trim_trailing_whitespace = false
 

README.md

@@ -297,11 +297,22 @@ Copyright © 2014-2020, [Aaron Bull Schaefer](mailto:[email protected]).
 
 ## Contributing
 
+### Linting and formatting
+
+Please use:
+
+- the [shellcheck](https://www.shellcheck.net) tool to check for subtle bash
+  scripting errors in the _transcrypt_ file, and apply the recommendations when
+  possible. E.g: `shellcheck transcrypt`
+- the [shfmt](https://github.com/mvdan/sh) tool to apply consistent formatting
+  to the _transcrypt_ file, e.g: `shfmt -w transcrypt`
+- the [Prettier](https://prettier.io) tool to apply consistent formatting to the
+  _README.md_ file, e.g: `prettier --write README.md`
+
 ### Tests
 
 Tests are written using [bats-core](https://github.com/bats-core/bats-core)
-version of "Bash Automated Testing System" and stored in the *tests/*
-directory.
+version of "Bash Automated Testing System" and stored in the _tests/_ directory.
 
 To run the tests:
 
@@ -313,12 +324,12 @@ To run the tests:
 
 Fixes:
 
-- Fix handling of branch merges with conflicts in encrypted files, which
-  would previously leave the user to manually merge files with a mix of
-  encrypted and unencrypted content.
+- Fix handling of branch merges with conflicts in encrypted files, which would
+  previously leave the user to manually merge files with a mix of encrypted and
+  unencrypted content.
 
   To apply this fix in projects that already use transcrypt: uninstall and
-  re-init transcrypt, then add `merge=crypt` to the patterns in *.gitattributes*
+  re-init transcrypt, then add `merge=crypt` to the patterns in _.gitattributes_
 
 Improvements:
 

transcrypt

@@ -436,6 +436,7 @@ save_configuration() {
 		git config filter.crypt.smudge '"$(git rev-parse --git-common-dir)"/crypt/smudge'
 		# shellcheck disable=SC2016
 		git config diff.crypt.textconv '"$(git rev-parse --git-common-dir)"/crypt/textconv'
+		# shellcheck disable=SC2016
 		git config merge.crypt.driver '"$(git rev-parse --git-common-dir)"/crypt/merge %O %A %B %L %P'
 	else
 		# shellcheck disable=SC2016
@@ -444,6 +445,7 @@ save_configuration() {
 		git config filter.crypt.smudge '"$(git rev-parse --git-dir)"/crypt/smudge'
 		# shellcheck disable=SC2016
 		git config diff.crypt.textconv '"$(git rev-parse --git-dir)"/crypt/textconv'
+		# shellcheck disable=SC2016
 		git config merge.crypt.driver '"$(git rev-parse --git-dir)"/crypt/merge %O %A %B %L %P'
 	fi
 	git config filter.crypt.required 'true'