stdlib/os: handle symlinks in copy/move functions (#16709)

* stdlib/os: handle symlinks in copy/move functions

- Added optional `options` argument to `copyFile`, `copyFileToDir`, and
  `copyFileWithPermissions`. By default, symlinks are followed (copy files
  symlinks point to).
- `copyDir` and `copyDirWithPermissions` copy symlinks as symlinks (instead of
  skipping them as it was before).
- `moveFile` and `moveDir` move symlinks as symlinks (instead of skipping them
  sometimes as it was before).
- Added optional `followSymlinks` argument to `setFilePermissions`.

See also: nim-lang/RFCs#319

Co-authored-by: Timothee Cour <[email protected]>

* Address comments in #16709

Co-authored-by: Timothee Cour <[email protected]>

* Address comments in #16709 (second iteration)

Skip symlinks on Windows.

Co-authored-by: Timothee Cour <[email protected]>

Author: rominf

changelog.md

@@ -112,6 +112,18 @@ with other backends. see #9125. Use `-d:nimLegacyJsRound` for previous behavior.
 
 - Removed the optional `longestMatch` parameter of the `critbits._WithPrefix` iterators (it never worked reliably)
 
+
+- Added optional `options` argument to `copyFile`, `copyFileToDir`, and
+  `copyFileWithPermissions`. By default, on non-Windows OSes, symlinks are
+  followed (copy files symlinks point to); on Windows, `options` argument is
+  ignored and symlinks are skipped.
+- On non-Windows OSes, `copyDir` and `copyDirWithPermissions` copy symlinks as
+  symlinks (instead of skipping them as it was before); on Windows symlinks are
+  skipped.
+- On non-Windows OSes, `moveFile` and `moveDir` move symlinks as symlinks
+  (instead of skipping them sometimes as it was before).
+- Added optional `followSymlinks` argument to `setFilePermissions`.
+
 ## Language changes
 
 - `nimscript` now handles `except Exception as e`.

lib/posix/posix.nim

@@ -586,6 +586,8 @@ proc fstatvfs*(a1: cint, a2: var Statvfs): cint {.
   importc, header: "<sys/statvfs.h>".}
 
 proc chmod*(a1: cstring, a2: Mode): cint {.importc, header: "<sys/stat.h>", sideEffect.}
+when defined(osx) or defined(freebsd):
+  proc lchmod*(a1: cstring, a2: Mode): cint {.importc, header: "<sys/stat.h>", sideEffect.}
 proc fchmod*(a1: cint, a2: Mode): cint {.importc, header: "<sys/stat.h>", sideEffect.}
 proc fstat*(a1: cint, a2: var Stat): cint {.importc, header: "<sys/stat.h>", sideEffect.}
 proc lstat*(a1: cstring, a2: var Stat): cint {.importc, header: "<sys/stat.h>", sideEffect.}