rename: Add error.CircularLoop

Adds error.CircularLoop to rename functions.

According to the man page for rename, "EINVAL The old pathname names
an ancestor directory of the new pathname, or either pathname argument
contains a final component that is dot or dot-dot." The later is always
programmer error, so returning error.CircularLoop should always be
correct.

Based on empirical testing, SHARING_VIOLATION is returned by Windows to
indicate a circular loop.

Author: gooncreeper

lib/std/fs/test.zig

@@ -991,6 +991,30 @@ test "Dir.rename file <-> dir" {
     }.impl);
 }
 
+test "Dir.rename circular loop" {
+    try testWithAllSupportedPathTypes(struct {
+        fn impl(ctx: *TestContext) !void {
+            const parent_path = try ctx.transformPath("parent");
+            const subdir_path = try ctx.transformPath("parent/subdir");
+            try ctx.dir.makeDir(parent_path);
+            try testing.expectError(error.CircularLoop, ctx.dir.rename(parent_path, subdir_path));
+
+            if (ctx.path_type == .relative) {
+                var parent = try ctx.dir.openDir("parent", .{});
+                defer parent.close();
+                try testing.expectError(error.CircularLoop, parent.rename("../parent", "subdir"));
+            }
+
+            if (ctx.path_type == .absolute) {
+                try testing.expectError(error.CircularLoop, std.fs.renameAbsolute(
+                    parent_path,
+                    subdir_path,
+                ));
+            }
+        }
+    }.impl);
+}
+
 test "rename" {
     var tmp_dir1 = tmpDir(.{});
     defer tmp_dir1.cleanup();

lib/std/os/windows.zig

@@ -1121,7 +1121,12 @@ pub fn DeleteFile(sub_path_w: []const u16, options: DeleteFileOptions) DeleteFil
     }
 }
 
-pub const MoveFileError = error{ FileNotFound, AccessDenied, Unexpected };
+pub const MoveFileError = error{
+    FileNotFound,
+    AccessDenied,
+    CircularLoop,
+    Unexpected,
+};
 
 pub fn MoveFileEx(old_path: []const u8, new_path: []const u8, flags: DWORD) (MoveFileError || Wtf8ToPrefixedFileWError)!void {
     const old_path_w = try sliceToPrefixedFileW(null, old_path);
@@ -1134,6 +1139,7 @@ pub fn MoveFileExW(old_path: [*:0]const u16, new_path: [*:0]const u16, flags: DW
         switch (GetLastError()) {
             .FILE_NOT_FOUND => return error.FileNotFound,
             .ACCESS_DENIED => return error.AccessDenied,
+            .SHARING_VIOLATION => return error.CircularLoop,
             else => |err| return unexpectedError(err),
         }
     }

lib/std/posix.zig

@@ -2599,6 +2599,7 @@ pub const RenameError = error{
     FileBusy,
     DiskQuota,
     IsDir,
+    CircularLoop,
     SymLinkLoop,
     LinkQuotaExceeded,
     NameTooLong,
@@ -2662,7 +2663,7 @@ pub fn renameZ(old_path: [*:0]const u8, new_path: [*:0]const u8) RenameError!voi
         .BUSY => return error.FileBusy,
         .DQUOT => return error.DiskQuota,
         .FAULT => unreachable,
-        .INVAL => unreachable,
+        .INVAL => return error.CircularLoop,
         .ISDIR => return error.IsDir,
         .LOOP => return error.SymLinkLoop,
         .MLINK => return error.LinkQuotaExceeded,
@@ -2725,7 +2726,7 @@ fn renameatWasi(old: RelativePathWasi, new: RelativePathWasi) RenameError!void {
         .BUSY => return error.FileBusy,
         .DQUOT => return error.DiskQuota,
         .FAULT => unreachable,
-        .INVAL => unreachable,
+        .INVAL => return error.CircularLoop,
         .ISDIR => return error.IsDir,
         .LOOP => return error.SymLinkLoop,
         .MLINK => return error.LinkQuotaExceeded,
@@ -2777,7 +2778,7 @@ pub fn renameatZ(
         .BUSY => return error.FileBusy,
         .DQUOT => return error.DiskQuota,
         .FAULT => unreachable,
-        .INVAL => unreachable,
+        .INVAL => return error.CircularLoop,
         .ISDIR => return error.IsDir,
         .LOOP => return error.SymLinkLoop,
         .MLINK => return error.LinkQuotaExceeded,
@@ -2901,6 +2902,7 @@ pub fn renameatW(
         .DIRECTORY_NOT_EMPTY => return error.PathAlreadyExists,
         .FILE_IS_A_DIRECTORY => return error.IsDir,
         .NOT_A_DIRECTORY => return error.NotDir,
+        .SHARING_VIOLATION => return error.CircularLoop,
         else => return windows.unexpectedStatus(rc),
     }
 }

src/fmt.zig

@@ -222,6 +222,7 @@ const FmtError = error{
     NetNameDeleted,
     InvalidArgument,
     ProcessNotFound,
+    CircularLoop,
 } || fs.File.OpenError;
 
 fn fmtPath(fmt: *Fmt, file_path: []const u8, check_mode: bool, dir: fs.Dir, sub_path: []const u8) FmtError!void {