create binary symlinks with relative location

get.go

@@ -806,7 +806,8 @@ func install(ctx context.Context, logger *log.Logger, r *runner.Runner, modDir s
 	}
 
 	// go install does not define -modfile flag, so we mimic go install with go build -o instead.
-	binPath := filepath.Join(gobin, fmt.Sprintf("%s-%s", name, pkg.Module.Version))
+	binName := fmt.Sprintf("%s-%s", name, pkg.Module.Version)
+	binPath := filepath.Join(gobin, binName)
 
 	// New context with new environment files.
 	modCtx = r.With(ctx, modFile.Filepath(), modDir, pkg.BuildEnvs)
@@ -825,12 +826,19 @@ func install(ctx context.Context, logger *log.Logger, r *runner.Runner, modDir s
 		return nil
 	}
 
-	if err := os.RemoveAll(filepath.Join(gobin, name)); err != nil {
+	return installSymlink(gobin, binName, name)
+}
+
+func installSymlink(dir, oldName, newName string) error {
+	newPath := filepath.Join(dir, newName)
+	if err := os.RemoveAll(newPath); err != nil {
 		return errors.Wrap(err, "rm")
 	}
-	if err := os.Symlink(binPath, filepath.Join(gobin, name)); err != nil {
+
+	if err := os.Symlink(oldName, newPath); err != nil {
 		return errors.Wrap(err, "symlink")
 	}
+
 	return nil
 }
 

get_test.go

@@ -4,6 +4,8 @@
 package main
 
 import (
+	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/efficientgo/core/errors"
@@ -89,3 +91,38 @@ func TestParseTarget(t *testing.T) {
 	}
 
 }
+
+func TestInstallSymlink(t *testing.T) {
+	dir := t.TempDir()
+	oldName := "some-binary-1.2.3"
+	newName := "some-binary"
+	oldPath := filepath.Join(dir, oldName)
+	newPath := filepath.Join(dir, newName)
+	testData := "#!/bin/true"
+
+	// simulate an existing symlink to test the removal logic
+	f, err := os.Create(newPath)
+	testutil.Ok(t, err)
+	testutil.Ok(t, f.Close())
+
+	// create a dummy target ...
+	f, err = os.Create(oldPath)
+	testutil.Ok(t, err)
+	// ... and write some data for verification later
+	_, err = f.Write([]byte(testData))
+	testutil.Ok(t, err)
+	testutil.Ok(t, f.Close())
+
+	err = installSymlink(dir, oldName, newName)
+	testutil.Ok(t, err)
+
+	gotPath, err := os.Readlink(newPath)
+	testutil.Ok(t, err)
+	testutil.Equals(t, oldName, gotPath)
+
+	gotData, err := os.ReadFile(newPath)
+	testutil.Ok(t, err)
+
+	// ensure the symlink leads to the desired target
+	testutil.Equals(t, testData, string(gotData))
+}