cmd/go/internal/modload: address comment and test issues from CL 496635

Michael noticed some minor issues in backports of CL 496635.
Those issues have been addressed in the backport CLs; this change
applies them to the main branch as well.

Updates #60313.

Change-Id: If68696711a10a9270193df66ed551395c14cae00
Reviewed-on: https://go-review.googlesource.com/c/go/+/502695
Run-TryBot: Bryan Mills <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: Bryan C. Mills

src/cmd/go/internal/modload/buildlist.go

@@ -916,7 +916,7 @@ func tidyPrunedRoots(ctx context.Context, mainModule module.Version, old *Requir
 		var disambiguateRoot sync.Map
 		for _, pkg := range pkgs {
 			if pkg.mod.Path == "" || pathIsRoot[pkg.mod.Path] {
-				// Lazy module loading will cause m to be checked before any other modules
+				// Lazy module loading will cause pkg.mod to be checked before any other modules
 				// that are only indirectly required. It is as unambiguous as possible.
 				continue
 			}

src/cmd/go/testdata/script/mod_tidy_issue60313.txt

@@ -21,7 +21,7 @@ require example.net/outer/inner v0.1.0 // indirect
 replace (
 	example.net/a v0.1.0 => ./a
 	example.net/b v0.1.0 => ./b
-	example.net/outer v0.1.0 => ./outer1
+	example.net/outer v0.1.0 => ./outer
 	example.net/outer/inner v0.1.0 => ./inner
 )
 -- example.go --
@@ -61,13 +61,9 @@ module example.net/outer/inner
 go 1.21
 -- inner/inner.go --
 package inner
--- outer1/go.mod --
+-- outer/go.mod --
 module example.net/outer
 
 go 1.21
--- outer1/inner/inner.go --
+-- outer/inner/inner.go --
 package inner
--- outer2/go.mod --
-module example.net/outer
-
-go 1.21