feat(version): update bump version script

bump_version.sh

@@ -66,12 +66,16 @@ Help()
    echo
    echo "The Portainer Agent version is in the semantic version format:"
    echo "    X.Y.Z (Major.Minor.Patch)"
+   echo "A alpha version is indicated by a pre-release tag:"
+   echo "    X.Y.Z-alpha.1 (Major.Minor.Patch-alpha.Revision)"
    echo "A beta version is indicated by a pre-release tag:"
    echo "    X.Y.Z-beta.0 (Major.Minor.Patch-beta.Revision)"
    echo
    echo "The order of bumping is:"
-   echo "x.x.x -> x.x+1.0-beta.1 -> x.x+1.0-beta.1 -> x.x+1.0"
-   echo "(2.19.0 -> 2.19.1 -> 2.20.0-beta.1 -> 2.20.0-beta.2 -> 2.20.0)"
+   echo "x.x.x -> x.x+1.0-alpha.1 -> x.x+1.0-alpha.2 -> x.x+1.0-beta.1 ->"
+   echo "x.x+1.0-beta.2 -> x.x+1.0 -> x.x+1.1"
+   echo "For example, bumping from 2.19.0 to 2.20.0 would be:"
+   echo "(2.19.0 -> 2.19.1 -> 2.20.0-alpha.1 -> 2.20.0-beta.1 -> 2.20.0)"
    echo
    echo "The current version is defined in multiple files."
    echo "This script will update the version in the following files:"
@@ -107,10 +111,16 @@ patch=${a[2]}
 
 len=${#a[@]}
 if [[ $len > 3 ]]; then
-    NEW_VERSION="${major}.${minor}.${patch}"
+    pre_release=${a[3]}
+
+    if [[ $pre_release == "alpha"* ]]; then
+        NEW_VERSION="${major}.${minor}.${patch}-beta.1"
+    elif [[ $pre_release == "beta"* ]]; then
+        NEW_VERSION="${major}.${minor}.${patch}"
+    fi
 else
     if IsReleaseBranch; then 
-        NEW_VERSION="${major}.${minor}.${patch}-beta.1"
+        NEW_VERSION="${major}.${minor}.${patch}-alpha.1"
     else 
         minor=$((minor+1))
         NEW_VERSION="${major}.${minor}.${patch}"