Add option to version command to output version number only

Resolves: #1407

docs/docs/cli.md

@@ -423,6 +423,9 @@ bump rule is provided.
 The new version should ideally be a valid semver string or a valid bump rule:
 `patch`, `minor`, `major`, `prepatch`, `preminor`, `premajor`, `prerelease`.
 
+## Options
+
+* `--short (-s)`: Output the version number only.
 
 ## export
 

poetry/console/commands/version.py

 from cleo import argument
+from cleo import option
 
 from .command import Command
 
@@ -18,6 +19,7 @@ class VersionCommand(Command):
             optional=True,
         )
     ]
+    options = [option("short", "s", "Output the version number only")]
 
     help = """\
 The version command shows the current version of the project or bumps the version of
@@ -58,11 +60,14 @@ patch, minor, major, prepatch, preminor, premajor, prerelease.
 
             self.poetry.file.write(content)
         else:
-            self.line(
-                "<comment>{}</> <info>{}</>".format(
-                    self.poetry.package.name, self.poetry.package.pretty_version
+            if self.option("short"):
+                self.line("{}".format(self.poetry.package.pretty_version))
+            else:
+                self.line(
+                    "<comment>{}</> <info>{}</>".format(
+                        self.poetry.package.name, self.poetry.package.pretty_version
+                    )
                 )
-            )
 
     def increment_version(self, version, rule):
         from poetry.core.semver import Version

tests/console/commands/test_version.py

@@ -45,3 +45,10 @@ def test_version_show(app):
     tester = CommandTester(command)
     tester.execute()
     assert "simple-project 1.2.3\n" == tester.io.fetch_output()
+
+
+def test_short_version_show(app):
+    command = app.find("version")
+    tester = CommandTester(command)
+    tester.execute("--short")
+    assert "1.2.3\n" == tester.io.fetch_output()