Make two-way variable replacement case-insensitive

The conversion from a known path prefix to a variable is now done in a
case-insensitive way. This means that if the variable `{storage}` has
value `S:\Flamenco`, a path `s:\flamenco\project\file.blend` will be
recognised and replaced with `{storage}\project\file.blend`.

This happens uniformly, regardless of the platform. So also on Linux,
which has a case-sensitive filesystem, this matching is done in a
case-insensitive way. It is very unlikely that a Flamenco configuration
has two separate variables, for paths that only differ in their case.

Fixes: #104336 Drive letter case mismatch causes two way variables not
to work correctly

internal/manager/config/variables.go

@@ -50,11 +50,15 @@ func (c *Conf) NewVariableExpander(audience VariableAudience, platform VariableP
 // ValueToVariableReplacer replaces any variable values it recognises in
 // valueToConvert to the actual variable. For example, `/path/to/file.blend` can
 // be changed to `{my_storage}/file.blend`.
+//
+// Matching is done in a case-insensitive way on all platforms, because some
+// filesystems are case-insensitive. It is very unlikely that there will be two
+// variables for two paths, only differing in their case.
 func (vvc *ValueToVariableReplacer) Replace(valueToConvert string) string {
 	result := valueToConvert
 
 	for varName, varValue := range vvc.twoWayVars {
-		if !isValueMatch(result, varValue) {
+		if !isValueMatch(strings.ToLower(result), strings.ToLower(varValue)) {
 			continue
 		}
 		result = vvc.join(varName, result[len(varValue):])

internal/manager/config/variables_test.go

@@ -50,3 +50,29 @@ func TestExpandTwowayVariablesMixedSlashes(t *testing.T) {
 	assert.Equal(t, `/shared/flamenco/shot/file.blend`, expanderLnx.Expand(`{shared}\shot\file.blend`))
 	assert.Equal(t, `/shared/flamenco/shot/file.blend`, expanderLnx.Expand(`{shared}/shot/file.blend`))
 }
+
+func TestReplaceTwowayVariablesMixedCase(t *testing.T) {
+	c := DefaultConfig(func(c *Conf) {
+		c.Variables["shared"] = Variable{
+			IsTwoWay: true,
+			Values: []VariableValue{
+				{Value: "/shared/flamenco", Platform: VariablePlatformLinux},
+				{Value: `Y:\shared\flamenco`, Platform: VariablePlatformWindows},
+			},
+		}
+	})
+
+	replacerWin := c.NewVariableToValueConverter(VariableAudienceWorkers, VariablePlatformWindows)
+
+	// Both uppercase and lowercase drive letter should match.
+	assert.Equal(t, `{shared}\shot\file.blend`, replacerWin.Replace(`y:\shared\flamenco\shot\file.blend`),
+		"Lower-case drive letter should match")
+	assert.Equal(t, `{shared}\shot\file.blend`, replacerWin.Replace(`Y:\shared\flamenco\shot\file.blend`),
+		"Same-case drive letter should match")
+
+	// Both uppercase and lowercase path should match.
+	assert.Equal(t, `{shared}\shot\file.blend`, replacerWin.Replace(`Y:\SHARED\flamenco\shot\file.blend`),
+		"Upper case 1st directory component should match")
+	assert.Equal(t, `{shared}\SHOT\file.blend`, replacerWin.Replace(`Y:\shared\FLAMENCO\SHOT\file.blend`),
+		"Upper case 2nd directory component should match")
+}