Deprecate the -source command.

NEXT-RELEASE.md

@@ -14,6 +14,8 @@ or compiled, even if it is not executed:
 
 -   The `has-suffix` command is now deprecated. Use `str:has-suffix` instead.
 
+-   The `-source` command is now deprecated. Use `eval` instead.
+
 The following deprecated features trigger a warning when the code is evaluated:
 
 -   Using `:` in slice indicies is deprecated. Use `..` instead.

pkg/eval/builtin_fn_misc.go

@@ -251,6 +251,8 @@ func nextEvalCount() int {
 //
 // Read the named file, and evaluate it in the current scope.
 //
+// This function is deprecated. Use [eval](#eval) instead.
+//
 // Examples:
 //
 // ```elvish-transcript

pkg/eval/compiler.go

@@ -152,6 +152,8 @@ func (cp *compiler) checkDeprecatedBuiltin(name string, r diag.Ranger) {
 	}
 	msg := ""
 	switch name {
+	case "-source~":
+		msg = `the "source" command is deprecated; use "eval" instead`
 	case "ord~":
 		msg = `the "ord" command is deprecated; use "str:to-codepoints" instead`
 	case "chr~":