Add the new "add" command

Closes ponylang#34.

README.md

@@ -42,6 +42,13 @@ changelog-tool get 0.2.2
 changelog-tool unreleased -e
 ```
 
+## Add an entry to an unreleased section
+```bash
+changelog-tool add fixed "We fixed some bad issues" -e
+changelog-tool add added "We just added some new cool stuff" -e
+changelog-tool add changed "And changed things a bit" -e
+```
+
 ## Prepare a Changelog for a Release
 ```bash
 changelog-tool release 0.13.1

changelog-tool/changelog.pony

@@ -45,6 +45,11 @@ class Changelog
       unreleased = Release._unreleased()
     end
 
+  fun ref add_entry(section_name: String, entry: String) ? =>
+    match unreleased
+    | let r: Release => r.add_entry(section_name, entry)?
+    end
+
   fun string(): String iso^ =>
     let str = (recover String end)
       .> append("# Change Log\n\n")
@@ -79,25 +84,25 @@ class Release
     added = Section._empty(Added)
     changed = Section._empty(Changed)
 
+  fun ref add_entry(section_name: String, entry: String) ? =>
+    let section =
+      match section_name
+      | "fixed" => try fixed as Section else fixed = Section._empty(Fixed); fixed as Section end
+      | "added" => try added as Section else added = Section._empty(Added); added as Section end
+      | "changed" => try changed as Section else changed = Section._empty(Changed); changed as Section end
+      else error
+      end
+    section.entries.push("- " + entry)
+
   fun string(): String iso^ =>
-    if heading == _unreleased_heading then
-      "\n\n".join(
-        [ heading
-          "### Fixed\n"
-          "### Added\n"
-          "### Changed\n"
-          ""
-        ].values())
-    else
-      let str = recover String .> append(heading) .> append("\n\n") end
-      for section in [fixed; added; changed].values() do
-        match section
-        | let s: Section box =>
-          str .> append(s.string()) .> append("\n")
-        end
+    let str = recover String .> append(heading) .> append("\n\n") end
+    for section in [fixed; added; changed].values() do
+      match section
+      | let s: Section box =>
+        str .> append(s.string()) .> append("\n")
       end
-      str
     end
+    str
 
 class Section
   let label: TSection

changelog-tool/main.pony

@@ -70,6 +70,13 @@ actor Main
             ].values()),
           [edit],
           [ArgSpec.string("version")])?
+	CommandSpec.leaf(
+	  "add",
+	  "Add a new entry at the end of the section",
+	  [edit],
+	  [ ArgSpec.string("section")
+            ArgSpec.string("entry")
+	  ])?
       ])?
       .> add_help("help", "Print this message and exit")?
 
@@ -95,6 +102,8 @@ actor Main
     | "changelog-tool/release" =>
       cmd_release(
         path, filename, cmd.arg("version").string(), cmd.option("edit").bool())
+    | "changelog-tool/add" =>
+      cmd_add(path, filename, cmd.arg("section").string(), cmd.arg("entry").string(), cmd.option("edit").bool())
     else
       err("unknown command: " + cmd.fullname())
       please_report()
@@ -171,6 +180,24 @@ actor Main
       err("unable to perform release preparation")
     end
 
+  fun cmd_add(
+    filepath: FilePath,
+    filename: String,
+    section: String,
+    entry: String,
+    edit: Bool)
+  =>
+    try
+      edit_or_print(
+        filepath,
+        edit,
+	Changelog(parse(filepath, filename)?)?
+	  .> add_entry(section, entry)?
+	  .string())
+    else
+      err("unable add a new changelog entry")
+    end
+
   fun parse(filepath: FilePath, filename: String): peg.AST ? =>
     let source = peg.Source(filepath)?
     match recover val ChangelogParser().parse(source) end

tests/main.pony

@@ -232,6 +232,39 @@ class iso _TestRelease is UnitTest
 
       """)?
 
+    _ReleaseTestAfterAddingSomeEntries(h, ChangelogParser()).run(
+      """
+      # Change Log
+
+      ## [unreleased] - unreleased
+
+      ### Fixed
+
+      ### Added
+
+      ### Changed
+
+      """,
+      """
+      # Change Log
+
+      ## [0.0.0] - 0000-00-00
+
+      ### Fixed
+
+      - We made some fixes...
+      - Oh, and we made a final one.
+
+      ### Added
+
+      - We added some stuff as well.
+
+      ### Changed
+
+      - And we changed a few things also.
+
+      """)?
+
 class ParseTest
   let _h: TestHelper
   let _parser: Parser
@@ -286,6 +319,40 @@ class _ReleaseTest
       _h.fail()
     end
 
+class _ReleaseTestAfterAddingSomeEntries
+  let _h: TestHelper
+  let _parser: Parser
+
+  new create(h: TestHelper, parser: Parser) =>
+    (_h, _parser) = (h, parser)
+
+  fun run(input: String, expected: String) ? =>
+    let source = Source.from_string(input)
+    match recover val _parser.parse(source) end
+    | (let n: USize, let r: (AST | Token | NotPresent)) =>
+      match r
+      | let ast: AST =>
+        _h.log(recover val _Printer(ast) end)
+        // _h.log(Changelog(ast)?.string())
+        let changelog = Changelog(ast)?
+          .> add_entry("fixed", "We made some fixes...\n")?
+          .> add_entry("fixed", "Oh, and we made a final one.\n")?
+          .> add_entry("added", "We added some stuff as well.\n")?
+          .> add_entry("changed", "And we changed a few things also.\n")?
+	  .> create_release("0.0.0", "0000-00-00")
+        let output: String = changelog.string()
+        _h.log(output)
+        _h.assert_eq[String](expected, output)
+      else
+        _h.log(recover val _Printer(r) end)
+        _h.fail()
+      end
+    | (let offset: USize, let r: Parser val) =>
+      let e = recover val SyntaxError(source, offset, r) end
+      _Logv(_h, PegFormatError.console(e))
+      _h.fail()
+    end
+
 primitive _Logv
   fun apply(h: TestHelper, bsi: ByteSeqIter) =>
     let str = recover String end