feat: source convert uses api version when it exists

Author: mshanemc

messages/convert.source.md

@@ -20,6 +20,10 @@ To specify a package name that includes spaces, enclose the name in single quote
 
   $ <%= config.bin %> <%= command.id %> --root-dir path/to/source --output-dir path/to/outputdir --package-name 'My Package'
 
+# flags.api-version.summary
+
+API Version to use in the generated project's manifest. By default, will use the version from sfdx-project.json
+
 # flags.root-dir.summary
 
 Source directory other than the default package to convert.

src/commands/project/convert/source.ts

@@ -39,7 +39,7 @@ export class Source extends SfCommand<ConvertResultJson> {
   public static readonly aliases = ['force:source:convert'];
   public static readonly deprecateAliases = true;
   public static readonly flags = {
-    'api-version': orgApiVersionFlagWithDeprecations,
+    'api-version': { ...orgApiVersionFlagWithDeprecations, summary: messages.getMessage('flags.api-version.summary') },
     loglevel,
     'root-dir': Flags.directory({
       aliases: ['rootdir'],
@@ -117,7 +117,7 @@ export class Source extends SfCommand<ConvertResultJson> {
     }
 
     this.componentSet = await ComponentSetBuilder.build({
-      sourceapiversion: await getSourceApiVersion(),
+      sourceapiversion: this.flags['api-version'] ?? (await getSourceApiVersion()),
       sourcepath: paths,
       manifest: manifest
         ? {