miqt-docker: perform cygpath conversion

cmd/miqt-docker/filepath.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"path/filepath"
+	"regexp"
 	"runtime"
 	"strings"
 )
@@ -62,3 +63,30 @@ func highestCommonParent(paths []string) (string, error) {
 
 	return strings.Join(parts, string(filepath.Separator)), nil
 }
+
+// maybeTransformCygpath converts a Cygwin or MSYS2 path to a Windows path
+// that the path/filepath package will understand.
+// This is to handle the case where `git` in $PATH is a Cygwin binary instead
+// of a native one.
+func maybeTransformCygpath(s string) string {
+	if runtime.GOOS == "windows" {
+
+		// Cygwin
+		// Paths of the form /cygdrive/c/Users/username/Desktop/
+		if strings.HasPrefix(s, `/cygdrive/`) {
+			parts := strings.Split(s[1:], `/`) // skip first slash
+			return strings.ToUpper(parts[1]) + `:\` + strings.Join(parts[2:], `\`)
+		}
+
+		// MSYS2
+		// Paths of the form /c/Users/username/Desktop/
+		if regexp.MustCompile(`^/[a-z]/`).MatchString(s) {
+			parts := strings.Split(s[1:], `/`) // skip first slash
+			return strings.ToUpper(parts[0]) + `:\` + strings.Join(parts[1:], `\`)
+		}
+
+	}
+
+	// Not an affected path, or, non-Windows OS
+	return s
+}

cmd/miqt-docker/filepath_test.go

@@ -76,3 +76,61 @@ func TestHighestCommonParent(t *testing.T) {
 		}
 	}
 }
+
+func TestTransformCygpath(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skip("Cygpath transforms are GOOS=windows only")
+	}
+
+	type testCase struct {
+		input  string
+		expect string
+	}
+
+	cases := []testCase{
+
+		// No transform, no trailing slash
+		testCase{
+			input:  `C:\normal\windows\path`,
+			expect: `C:\normal\windows\path`,
+		},
+
+		// No transform, has trailing slash
+		testCase{
+			input:  `C:\normal\windows\path\`,
+			expect: `C:\normal\windows\path\`,
+		},
+
+		// Cygwin, no trailing slash
+		testCase{
+			input:  `/cygdrive/c/normal/windows/path`,
+			expect: `C:\normal\windows\path`,
+		},
+
+		// Cygwin, has trailing slash
+		testCase{
+			input:  `/cygdrive/c/normal/windows/path/`,
+			expect: `C:\normal\windows\path\`,
+		},
+
+		// MSYS2, no trailing slash
+		testCase{
+			input:  `/f/normal/windows/path`,
+			expect: `F:\normal\windows\path`,
+		},
+
+		// MSYS2, has trailing slash
+		testCase{
+			input:  `/f/normal/windows/path/`,
+			expect: `F:\normal\windows\path\`,
+		},
+	}
+
+	for idx, tc := range cases {
+		got := maybeTransformCygpath(tc.input)
+		if got != tc.expect {
+			t.Errorf("test %d: input(%v) got %q, want %q", idx, tc.input, got, tc.expect)
+		}
+	}
+
+}

cmd/miqt-docker/main.go

@@ -216,7 +216,9 @@ func getDockerRunArgsForGlob(dockerfiles []fs.DirEntry, containerNameGlob string
 		// Don't panic
 	} else {
 		if gitroot_sz := strings.TrimSpace(string(gitroot)); len(gitroot_sz) > 0 {
-			parentPaths = append(parentPaths, gitroot_sz)
+			// On Windows, sometimes Cygwin/MSYS git is in $PATH, which returns
+			// a special kind of filepath that requires conversion to use
+			parentPaths = append(parentPaths, maybeTransformCygpath(gitroot_sz))
 		}
 	}