Handle file casing when creating program

[sheetalkamat]

Handle file casing when creating program so that we dont add duplicate files that only differ in casing on case insesitive file system.
This also adds checks for forceConsistentCasingInFileNames

Fixes #1549
Fixes #1619

[Copilot]

Pull request overview

This PR implements file casing handling for case-insensitive file systems to prevent duplicate files that only differ in casing and adds checks for the forceConsistentCasingInFileNames compiler option.

• Adds a new utility function GetNormalizedAbsolutePathWithoutRoot to strip root paths for casing comparison
• Refactors the file parser to track files by both path and casing, allowing detection of duplicate files with different casings
• Implements diagnostic reporting for files that differ only in casing (TS1149 and TS1261)

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
testdata/baselines/reference/tsc/incremental/Compile-incremental-with-case-insensitive-file-names.js	New baseline test for incremental compilation with case-insensitive file names
testdata/baselines/reference/tsc/forceConsistentCasingInFileNames/*.js	New baseline tests covering various forceConsistentCasingInFileNames scenarios
internal/tspath/path_test.go	Adds test for GetNormalizedAbsolutePathWithoutRoot function
internal/tspath/path.go	Implements GetNormalizedAbsolutePathWithoutRoot to strip root from absolute paths
internal/execute/tsctests/tsc_test.go	Adds comprehensive test cases for forceConsistentCasingInFileNames feature
internal/execute/incremental/snapshottobuildinfo.go	Changes MapNonNil to Map and removes duplicate file filtering logic
internal/compiler/processingDiagnostic.go	Prevents duplicate related info when the preferred location is the same as the include reason
internal/compiler/includeprocessor.go	Adds addProcessingDiagnosticsForFileCasing to generate appropriate casing error diagnostics
internal/compiler/filesparser.go	Major refactor to track files by casing, detect duplicates, and generate casing diagnostics
internal/compiler/fileloader.go	Moves file collection logic into filesParser.getProcessedFiles()

[Copilot]

Loop variable capture issue: The task and i variables are captured in the closure passed to w.wg.Queue(), but the loop continues to modify these variables. This means all goroutines will see the final values of task and i from the loop, not the values from when the closure was created.

To fix this, capture the loop variables in the loop scope:

for i, task := range tasks {
    i := i
    task := task
    task.path = loader.toPath(task.normalizedFilePath)
    // ... rest of the code
}

[Copilot]

Typo in test case: "worspaces" should be "workspaces".

Suggested change

	assert.Equal(t, GetNormalizedAbsolutePathWithoutRoot("c:/work/hello.txt", "d:/worspaces"), "work/hello.txt")
	assert.Equal(t, GetNormalizedAbsolutePathWithoutRoot("c:/work/hello.txt", "d:/workspaces"), "work/hello.txt")

[Copilot]

Grammar issue in comment: Missing semicolon/period, and "its" should be "it's".

Suggested change

	// Check if it differs only in drive letters its ok to ignore that error:
	// Check if it differs only in drive letters; it's ok to ignore that error.

[gabritto]

To make sure I understand this, why can't this check be made above along with the check for when ForceConsistentCasingInFileNames is true?