Add test cases for init command

These changes include a series of test cases for validating packer init
using the force and upgrade flag. Include in this test is a test case
for validating the plugin installation error when init encounters a
plugin whose reported version does not match the version within the
plugin name.

```
--- PASS: Test_PackerCoreSuite (18.66s)
    --- PASS: Test_PackerCoreSuite/TestPackerInitForce (4.91s)
        --- PASS: Test_PackerCoreSuite/TestPackerInitForce/installs_any_missing_plugins (2.76s)
        --- PASS: Test_PackerCoreSuite/TestPackerInitForce/reinstalls_plugins_matching_version_constraints (2.14s)
    --- PASS: Test_PackerCoreSuite/TestPackerInitUpgrade (3.70s)
        --- PASS: Test_PackerCoreSuite/TestPackerInitUpgrade/upgrades_a_plugin_to_the_latest_matching_version_constraints (2.02s)
    --- PASS: Test_PackerCoreSuite/TestPackerInitWithMixedVersions (1.96s)
        --- PASS: Test_PackerCoreSuite/TestPackerInitWithMixedVersions/skips_the_plugin_installation_with_mixed_versions_before_exiting_with_an_error (1.96s)
    --- PASS: Test_PackerCoreSuite/TestPackerInitWithNonGithubSource (1.22s)
        --- PASS: Test_PackerCoreSuite/TestPackerInitWithNonGithubSource/try_installing_from_a_non-github_source,_should_fail (0.07s)
        --- PASS: Test_PackerCoreSuite/TestPackerInitWithNonGithubSource/manually_install_plugin_to_the_expected_source (0.59s)
        --- PASS: Test_PackerCoreSuite/TestPackerInitWithNonGithubSource/re-run_packer_init_on_same_template,_should_succeed_silently (0.55s)
```

packer_test/init_test.go

@@ -0,0 +1,74 @@
+package packer_test
+
+func (ts *PackerTestSuite) TestPackerInitForce() {
+	pluginPath, cleanup := ts.MakePluginDir()
+	defer cleanup()
+
+	ts.Run("installs any missing plugins", func() {
+		ts.PackerCommand().UsePluginDir(pluginPath).
+			SetArgs("init", "--force", "./templates/init/hashicups.pkr.hcl").
+			Assert(MustSucceed(), Grep("Installed plugin github.com/hashicorp/hashicups v1.0.2", grepStdout))
+	})
+
+	ts.Run("reinstalls plugins matching version constraints", func() {
+		ts.PackerCommand().UsePluginDir(pluginPath).
+			SetArgs("init", "--force", "./templates/init/hashicups.pkr.hcl").
+			Assert(MustSucceed(), Grep("Installed plugin github.com/hashicorp/hashicups v1.0.2", grepStdout))
+	})
+}
+
+func (ts *PackerTestSuite) TestPackerInitUpgrade() {
+	pluginPath, cleanup := ts.MakePluginDir()
+	defer cleanup()
+
+	cmd := ts.PackerCommand().UsePluginDir(pluginPath)
+	cmd.SetArgs("plugins", "install", "github.com/hashicorp/hashicups", "1.0.1")
+	cmd.Assert(MustSucceed(), Grep("Installed plugin github.com/hashicorp/hashicups v1.0.1", grepStdout))
+
+	_, _, err := cmd.Run()
+	if err != nil {
+		ts.T().Fatalf("packer plugins install failed to install previous version of hashicups: %q", err)
+	}
+
+	ts.Run("upgrades a plugin to the latest matching version constraints", func() {
+		ts.PackerCommand().UsePluginDir(pluginPath).
+			SetArgs("init", "--upgrade", "./templates/init/hashicups.pkr.hcl").
+			Assert(MustSucceed(), Grep("Installed plugin github.com/hashicorp/hashicups v1.0.2", grepStdout))
+	})
+}
+
+func (ts *PackerTestSuite) TestPackerInitWithNonGithubSource() {
+	pluginPath, cleanup := ts.MakePluginDir()
+	defer cleanup()
+
+	ts.Run("try installing from a non-github source, should fail", func() {
+		ts.PackerCommand().UsePluginDir(pluginPath).
+			SetArgs("init", "./templates/init/non_gh.pkr.hcl").
+			Assert(MustFail(), Grep(`doesn't appear to be a valid "github.com" source address`, grepStdout))
+	})
+
+	ts.Run("manually install plugin to the expected source", func() {
+		ts.PackerCommand().UsePluginDir(pluginPath).
+			SetArgs("plugins", "install", "--path", BuildSimplePlugin("1.0.10", ts.T()), "hubgit.com/hashicorp/tester").
+			Assert(MustSucceed(), Grep("packer-plugin-tester_v1.0.10", grepStdout))
+	})
+
+	ts.Run("re-run packer init on same template, should succeed silently", func() {
+		ts.PackerCommand().UsePluginDir(pluginPath).
+			SetArgs("init", "./templates/init/non_gh.pkr.hcl").
+			Assert(MustSucceed(),
+				MkPipeCheck("no output in stdout").SetTester(ExpectEmptyInput()).SetStream(OnlyStdout))
+	})
+}
+
+func (ts *PackerTestSuite) TestPackerInitWithMixedVersions() {
+	pluginPath, cleanup := ts.MakePluginDir()
+	defer cleanup()
+
+	ts.Run("skips the plugin installation with mixed versions before exiting with an error", func() {
+		ts.PackerCommand().UsePluginDir(pluginPath).
+			SetArgs("init", "./templates/init/mixed_versions.pkr.hcl").
+			Assert(MustFail(),
+				Grep("binary reported a pre-release version of 10.7.3-dev", grepStdout))
+	})
+}

packer_test/install_test.go

@@ -84,27 +84,3 @@ func (ts *PackerTestSuite) TestRemoteInstallWithPluginsInstall() {
 			Assert(MustFail(), Grep("Remote installation of pre-release plugin versions is unsupported.", grepStdout))
 	})
 }
-
-func (ts *PackerTestSuite) TestInitWithNonGithubSource() {
-	pluginPath, cleanup := ts.MakePluginDir()
-	defer cleanup()
-
-	ts.Run("try installing from a non-github source, should fail", func() {
-		ts.PackerCommand().UsePluginDir(pluginPath).
-			SetArgs("init", "./templates/non_gh.pkr.hcl").
-			Assert(MustFail(), Grep(`doesn't appear to be a valid "github.com" source address`, grepStdout))
-	})
-
-	ts.Run("manually install plugin to the expected source", func() {
-		ts.PackerCommand().UsePluginDir(pluginPath).
-			SetArgs("plugins", "install", "--path", BuildSimplePlugin("1.0.10", ts.T()), "hubgit.com/hashicorp/tester").
-			Assert(MustSucceed(), Grep("packer-plugin-tester_v1.0.10", grepStdout))
-	})
-
-	ts.Run("re-run packer init on same template, should succeed silently", func() {
-		ts.PackerCommand().UsePluginDir(pluginPath).
-			SetArgs("init", "./templates/non_gh.pkr.hcl").
-			Assert(MustSucceed(),
-				MkPipeCheck("no output in stdout").SetTester(ExpectEmptyInput()).SetStream(OnlyStdout))
-	})
-}

packer_test/templates/init/hashicups.pkr.hcl

@@ -0,0 +1,9 @@
+packer {
+	required_plugins {
+		tester = {
+			source = "github.com/hashicorp/hashicups"
+			version = ">= 1.0.2"
+		}
+	}
+}
+

packer_test/templates/init/mixed_versions.pkr.hcl

@@ -0,0 +1,9 @@
+packer {
+	required_plugins {
+		tester = {
+			source = "github.com/mondoohq/cnspec"
+			version = "= 10.7.3" # plugin describe reports 10.7.x-dev so init must fail
+		}
+	}
+}
+