Add '-h', '--help' message.

deploy.sh

@@ -1,5 +1,42 @@
 #!/usr/bin/env bash
 set -o errexit #abort if any command fails
+me=$(basename "$0")
+
+read -r -d '' "help_message" <<EOF || true
+
+Deploy generated files to a git branch.
+
+Usage:
+
+  $me [<options>]
+
+Options:
+
+  -h, --help               Show this help information.
+  -v, --verbose            Increase verbosity. Useful for debugging.
+  -e, --allow-empty        Allow deployment of an empty directory.
+  -m, --message MESSAGE    Specify the message used when committing on the
+                           deploy branch.
+  -n, --no-hash            Don't append the source commit's hash to the deploy
+                           commit's message.
+  -c, --config-file PATH   Override default & environment variables' values
+                           with those in set in the file at 'PATH'.
+
+Variables:
+
+  * GIT_DEPLOY_DIR      Folder path containing the files to deploy.
+  * GIT_DEPLOY_BRANCH   Commit deployable files to this branch.
+  * GIT_DEPLOY_REPO     Push the deploy branch to this repository.
+
+These variables have default values defined in the script. The defaults can be
+overridden by environment variables. Any environment variables are overridden
+by values set in a '.env' file (if it exists), and in turn by those set in a
+file specified by the '--config-file' option.
+EOF
+
+print_help() {
+	printf "%s\n" "$help_message"
+}
 
 main() {
 	# Set args from a local environment file.
@@ -12,7 +49,10 @@ main() {
 
 	# Parse arg flags
 	while : ; do
-		if [[ $1 = "-v" || $1 = "--verbose" ]]; then
+		if [[ $1 = "-h" || $1 = "--help" ]]; then
+			print_help
+			return 0
+		elif [[ $1 = "-v" || $1 = "--verbose" ]]; then
 			verbose=true
 			shift
 		elif [[ $1 = "-e" || $1 = "--allow-empty" ]]; then

readme.md

@@ -37,6 +37,8 @@ Do this every time you want to deploy, or have your CI server do it.
 5. run `./deploy.sh`
 
 ### options
+`-h`, `--help`: show the program's help info.
+
 `-c`, `--config-file`: specify a file that overrides the script's default configuration, or those values set in `.env`. The syntax for this file should be normal `var=value` declarations.
 
 `-m`, `--message <message>`: specify message to be used for the commit on `deploy_branch`. By default, the message is the title of the source commit, prepended with 'publish: '.