add release script

Author: Vladimir Kotal

README.md

@@ -13,10 +13,5 @@ The class home page is https://devnull-cz.github.io/unix-linux-prog-in-c/
 ## Trigger new release
 
 ```
-# get the latest tag
-$ git tag | sed 's/^v//' | sort -n | tail -1
-# create new tag
-$ git tag v<XYZ>
-# push it to the repo
-$ git push origin v<XYZ>
+./dev/release.sh v<XYZ>
 ```

dev/release.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+#
+# Trigger new release creation on Github.
+#
+
+set -e
+
+if (( $# > 1 )); then
+	echo "usage: `basename $0` [version]"
+	exit 1
+fi
+
+# Get the latest version (needs curl + jq).
+if (( $# == 0 )); then
+	curl -s https://api.github.com/repos/devnull-cz/unix-linux-prog-in-c/releases/latest | \
+	    jq .tag_name
+	exit 0
+fi
+
+VERSION=$1
+
+if ! echo "$VERSION" | grep '^[0-9]\+\.[0-9]\+\.[0-9]\+$' >/dev/null; then
+	echo "version needs to be in the form of <num>.<num>.<num>"
+	exit 1
+fi
+
+ver=$( git tag -l "$VERSION" )
+if (( $? != 0 )); then
+	echo "Cannot determine tag"
+	exit 1
+fi
+if [[ $ver == $VERSION ]]; then
+	echo "Tag $VERSION already exists"
+	exit 1
+fi
+
+git pull --ff-only
+git tag "$VERSION"
+git push origin tag "$VERSION"