findGitBin(): memoize the result

Author: mhagger

git/git_bin.go

@@ -2,26 +2,41 @@ package git
 
 import (
 	"path/filepath"
+	"sync"
 
 	"github.com/cli/safeexec"
 )
 
+// This variable will be used to memoize the result of `findGitBin()`,
+// since its return value only depends on the environment.
+var gitBinMemo struct {
+	once sync.Once
+
+	gitBin string
+	err    error
+}
+
 // findGitBin finds the `git` binary in PATH that should be used by
 // the rest of `git-sizer`. It uses `safeexec` to find the executable,
 // because on Windows, `exec.Cmd` looks not only in PATH, but also in
 // the current directory. This is a potential risk if the repository
 // being scanned is hostile and non-bare because it might possibly
 // contain an executable file named `git`.
 func findGitBin() (string, error) {
-	gitBin, err := safeexec.LookPath("git")
-	if err != nil {
-		return "", err
-	}
+	gitBinMemo.once.Do(func() {
+		p, err := safeexec.LookPath("git")
+		if err != nil {
+			gitBinMemo.err = err
+			return
+		}
 
-	gitBin, err = filepath.Abs(gitBin)
-	if err != nil {
-		return "", err
-	}
+		p, err = filepath.Abs(p)
+		if err != nil {
+			gitBinMemo.err = err
+			return
+		}
 
-	return gitBin, nil
+		gitBinMemo.gitBin = p
+	})
+	return gitBinMemo.gitBin, gitBinMemo.err
 }