feat(StringUtil): implement format placeholders closer to _posix parameter expansion_ - i.e. implement optional colon

Author: iv601625

README.md

@@ -156,11 +156,11 @@ You can configure the version and properties adjustments for specific branches a
 
 ℹ Final `version` will be slugified automatically, so no need to use `${….slug}` placeholders in `<version>` format.
 
-ℹ define placeholder default value (placeholder is not defined) like this `${name:-DEFAULT_VALUE}`<br>
-e.g `${env.BUILD_NUMBER:-0}` or `${env.BUILD_NUMBER:-local}`
+ℹ define placeholder default value (placeholder is not defined '-' or empty ':-') like this `${name:-DEFAULT_VALUE}`<br>
+e.g `${env.BUILD_NUMBER-0}` or `${env.BUILD_NUMBER:-local}`
 
-ℹ define placeholder overwrite value (placeholder is defined) like this `${name:+OVERWRITE_VALUE}`<br>
-e.g `${dirty:-SNAPSHOT}` resolves to `-SNAPSHOT` instead of `-DIRTY`
+ℹ define placeholder overwrite value (placeholder is defined '+' and non-empty ':+' ) like this `${name:+OVERWRITE_VALUE}`<br>
+e.g `${dirty:+SNAPSHOT}` resolves to `-SNAPSHOT` instead of `-DIRTY`
 
 ###### Placeholders
 

src/main/java/me/qoomon/gitversioning/commons/StringUtil.java

@@ -12,7 +12,7 @@ public final class StringUtil {
 
     public static String substituteText(String text, Map<String, Supplier<String>> replacements) {
         StringBuffer result = new StringBuffer();
-        Pattern placeholderPattern = Pattern.compile("\\$\\{(?<key>[^}:]+)(?::(?<modifier>[-+])(?<value>[^}]*))?}");
+        Pattern placeholderPattern = Pattern.compile("\\$\\{(?<key>[^}:]+)(?<modifier>:?[-+])?(?<value>[^}]*)?}");
         Matcher placeholderMatcher = placeholderPattern.matcher(text);
         while (placeholderMatcher.find()) {
             String placeholderKey = placeholderMatcher.group("key");
@@ -26,6 +26,12 @@ public static String substituteText(String text, Map<String, Supplier<String>> r
                 if (placeholderModifier.equals("+") && replacement != null) {
                     replacement = placeholderMatcher.group("value");
                 }
+                if (placeholderModifier.equals(":-") && (replacement == null || replacement.isEmpty())) {
+                    replacement = placeholderMatcher.group("value");
+                }
+                if (placeholderModifier.equals(":+") && replacement != null && !replacement.isEmpty()) {
+                    replacement = placeholderMatcher.group("value");
+                }
             }
             if (replacement != null) {
                 // avoid group name replacement behaviour of replacement parameter value