Completion proposal support for complete jline parameter

- to allow completing single argument with multiple tab clicks,
  for example file paths.
- Backport #512
- Fixes #834

Author: MJ Gallego

spring-shell-autoconfigure/src/main/java/org/springframework/shell/boot/CompleterAutoConfiguration.java

@@ -63,7 +63,7 @@ public void complete(LineReader reader, ParsedLine line, List<Candidate> candida
 					p.description(),
 					null,
 					null,
-					true)
+					p.complete())
 				)
 				.forEach(candidates::add);
 		}

spring-shell-core/src/main/java/org/springframework/shell/CompletionProposal.java

@@ -49,6 +49,12 @@ public class CompletionProposal {
 	 */
 	private boolean dontQuote = false;
 
+	/**
+	 * Whether the proposal cant be completed further. By setting complete to false then it will not append an space
+	 * making it easier to continue tab completion
+	 */
+	private boolean complete = true;
+
 	public CompletionProposal(String value) {
 		this.value = this.displayText = value;
 	}
@@ -89,6 +95,16 @@ public CompletionProposal category(String category) {
 		return this;
 	}
 
+	public CompletionProposal complete(boolean complete) {
+		this.complete = complete;
+		return this;
+	}
+
+	public boolean complete() {
+		return complete;
+	}
+
+
 	public CompletionProposal dontQuote(boolean dontQuote) {
 		this.dontQuote = dontQuote;
 		return this;

spring-shell-standard/src/main/java/org/springframework/shell/standard/FileValueProvider.java

@@ -41,19 +41,23 @@ public class FileValueProvider implements ValueProvider {
 
 	@Override
 	public List<CompletionProposal> complete(CompletionContext completionContext) {
-        String input = completionContext.currentWordUpToCursor();
-        int lastSlash = input.lastIndexOf(File.separatorChar);
-        Path dir = lastSlash > -1 ? Paths.get(input.substring(0, lastSlash+1)) : Paths.get("");
-        String prefix = input.substring(lastSlash + 1, input.length());
+		String input = completionContext.currentWordUpToCursor();
+		int lastSlash = input.lastIndexOf(File.separatorChar);
+		Path dir = lastSlash > -1 ? Paths.get(input.substring(0, lastSlash + 1)) : Paths.get("");
+		String prefix = input.substring(lastSlash + 1);
 
-        try {
-            return Files
-                    .find(dir, 1, (p, a) -> p.getFileName() != null && p.getFileName().toString().startsWith(prefix),
-                            FOLLOW_LINKS)
-                    .map(p -> new CompletionProposal(p.toString()))
-                    .collect(Collectors.toList());
-        } catch (IOException e) {
-            throw new UncheckedIOException(e);
-        }
+		try {
+			return Files
+				.find(dir, 1, (p, a) -> p.getFileName() != null && p.getFileName().toString().startsWith(prefix),
+					FOLLOW_LINKS)
+				.map(p -> {
+					boolean directory = Files.isDirectory(p);
+					String value = p.toString() + (directory ? File.separatorChar : "");
+					return new CompletionProposal(value).complete(!directory);
+				})
+				.collect(Collectors.toList());
+		} catch (IOException e) {
+			throw new UncheckedIOException(e);
+		}
 	}
 }