[Emacs-diffs] master 2809012: Check case-sensitivity when renaming files

[Ken Brown]

branch: master
commit 2809012c8f9485d8dc54b186f989f289b2797892
Author: Ken Brown <address@hidden>
Commit: Ken Brown <address@hidden>

    Check case-sensitivity when renaming files
    
    * src/fileio.c (file_name_case_insensitive_p)
    (Ffile_name_case_insensitive_p):  New functions.
    (Frename_file): Allow renames that simply change case when the
    FILE argument is on a case-insensitive filesystem.  (Bug#24441)
    
    * lisp/dired-aux.el (dired-do-create-files): Use
    'file-name-case-insensitive-p' instead of 'system-type' to check
    for case-insensitivity.  (Bug#24441)
    
    * doc/lispref/files.texi (Truenames): Document
    'file-name-case-insensitive-p'.
---
 doc/lispref/files.texi |   17 +++++++++
 etc/NEWS               |    4 ++
 lisp/dired-aux.el      |   13 ++++---
 src/fileio.c           |   97 +++++++++++++++++++++++++++++++++++++++++-------
 4 files changed, 111 insertions(+), 20 deletions(-)

diff --git a/doc/lispref/files.texi b/doc/lispref/files.texi
index cb31ca5..70c7177 100644
--- a/doc/lispref/files.texi
+++ b/doc/lispref/files.texi
@@ -1140,6 +1140,23 @@ appropriate manner.  If @var{file1} or @var{file2} does 
not exist, the
 return value is unspecified.
 @end defun
 
address@hidden file-name-case-insensitive-p filename
+Sometimes file names or their parts need to be compared as strings, in
+which case it's important to know whether the underlying filesystem is
+case-insensitive.  This function returns @code{t} if file
address@hidden is on a case-insensitive filesystem.  It always returns
address@hidden on MS-DOS and MS-Windows.  On Cygwin and Mac OS X,
+filesystems may or may not be case-insensitive, and the function tries
+to determine case-sensitivity by a runtime test.  If the test is
+inconclusive, the function returns @code{t} on Cygwin and @code{nil}
+on Mac OS X.
+
+Currently this function always returns @code{nil} on platforms other
+than MS-DOS, MS-Windows, Cygwin, and Mac OS X.  It does not detect
+case-insensitivity of mounted filesystems, such as Samba shares or
+NFS-mounted Windows volumes.
address@hidden defun
+
 @defun file-in-directory-p file dir
 This function returns @code{t} if @var{file} is a file in directory
 @var{dir}, or in a subdirectory of @var{dir}.  It also returns
diff --git a/etc/NEWS b/etc/NEWS
index 197a694..fe76af5 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -62,6 +62,10 @@ affected by this, as SGI stopped supporting IRIX in December 
2013.
 * Changes in Emacs 26.1
 
 +++
+** The new function 'file-name-case-insensitive-p' tests whether a
+given file is on a case-insensitive filesystem.
+
++++
 ** The new user variable 'electric-quote-chars' provides a list
 of curved quotes for 'electric-quote-mode', allowing user to choose
 the types of quotes to be used.
diff --git a/lisp/dired-aux.el b/lisp/dired-aux.el
index 972b6b1..f94e053 100644
--- a/lisp/dired-aux.el
+++ b/lisp/dired-aux.el
@@ -1801,13 +1801,14 @@ Optional arg HOW-TO determines how to treat the target.
                     (concat (if dired-one-file op1 operation) " %s to: ")
                     target-dir op-symbol arg rfn-list default))))
         (into-dir (cond ((null how-to)
-                         ;; Allow DOS/Windows users to change the letter
-                         ;; case of a directory.  If we don't test these
-                         ;; conditions up front, file-directory-p below
-                         ;; will return t because the filesystem is
-                         ;; case-insensitive, and Emacs will try to move
+                         ;; Allow users to change the letter case of
+                         ;; a directory on a case-insensitive
+                         ;; filesystem.  If we don't test these
+                         ;; conditions up front, file-directory-p
+                         ;; below will return t on a case-insensitive
+                         ;; filesystem, and Emacs will try to move
                          ;; foo -> foo/foo, which fails.
-                         (if (and (memq system-type '(ms-dos windows-nt 
cygwin))
+                         (if (and (file-name-case-insensitive-p (car fn-list))
                                   (eq op-symbol 'move)
                                   dired-one-file
                                   (string= (downcase
diff --git a/src/fileio.c b/src/fileio.c
index d3da0fb..f3f8f42 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -25,6 +25,10 @@ along with GNU Emacs.  If not, see 
<http://www.gnu.org/licenses/>.  */
 #include <sys/stat.h>
 #include <unistd.h>
 
+#ifdef DARWIN_OS
+#include <sys/attr.h>
+#endif
+
 #ifdef HAVE_PWD_H
 #include <pwd.h>
 #endif
@@ -2232,6 +2236,72 @@ internal_delete_file (Lisp_Object filename)
   return NILP (tem);
 }
 
+/* Filesystems are case-sensitive on all supported systems except
+   MS-Windows, MS-DOS, Cygwin, and Mac OS X.  They are always
+   case-insensitive on the first two, but they may or may not be
+   case-insensitive on Cygwin and OS X.  The following function
+   attempts to provide a runtime test on those two systems.  If the
+   test is not conclusive, we assume case-insensitivity on Cygwin and
+   case-sensitivity on Mac OS X.
+
+   FIXME: Mounted filesystems on Posix hosts, like Samba shares or
+   NFS-mounted Windows volumes, might be case-insensitive.  Can we
+   detect this?  */
+
+static bool
+file_name_case_insensitive_p (const char *filename)
+{
+#ifdef DOS_NT
+  return 1;
+#elif defined CYGWIN
+/* As of Cygwin-2.6.1, pathconf supports _PC_CASE_INSENSITIVE.  */
+# ifdef _PC_CASE_INSENSITIVE
+  int res = pathconf (filename, _PC_CASE_INSENSITIVE);
+  if (res < 0)
+    return 1;
+  return res > 0;
+# else
+  return 1;
+# endif
+#elif defined DARWIN_OS
+  /* The following is based on
+     http://lists.apple.com/archives/darwin-dev/2007/Apr/msg00010.html.  */
+  struct attrlist alist;
+  unsigned char buffer[sizeof (vol_capabilities_attr_t) + sizeof (size_t)];
+
+  memset (&alist, 0, sizeof (alist));
+  alist.volattr = ATTR_VOL_CAPABILITIES;
+  if (getattrlist (filename, &alist, buffer, sizeof (buffer), 0)
+      || !(alist.volattr & ATTR_VOL_CAPABILITIES))
+    return 0;
+  vol_capabilities_attr_t *vcaps = buffer;
+  return !(vcaps->capabilities[0] & VOL_CAP_FMT_CASE_SENSITIVE);
+#else
+  return 0;
+#endif
+}
+
+DEFUN ("file-name-case-insensitive-p", Ffile_name_case_insensitive_p,
+       Sfile_name_case_insensitive_p, 1, 1, 0,
+       doc: /* Return t if file FILENAME is on a case-insensitive filesystem.
+The arg must be a string.  */)
+  (Lisp_Object filename)
+{
+  Lisp_Object handler;
+
+  CHECK_STRING (filename);
+  filename = Fexpand_file_name (filename, Qnil);
+
+  /* If the file name has special constructs in it,
+     call the corresponding file handler.  */
+  handler = Ffind_file_name_handler (filename, Qfile_name_case_insensitive_p);
+  if (!NILP (handler))
+    return call2 (handler, Qfile_name_case_insensitive_p, filename);
+
+  filename = ENCODE_FILE (filename);
+  return file_name_case_insensitive_p (SSDATA (filename)) ? Qt : Qnil;
+}
+
 DEFUN ("rename-file", Frename_file, Srename_file, 2, 3,
        "fRename file: \nGRename %s to file: \np",
        doc: /* Rename FILE as NEWNAME.  Both args must be strings.
@@ -2251,12 +2321,11 @@ This is what happens in interactive use with M-x.  */)
   file = Fexpand_file_name (file, Qnil);
 
   if ((!NILP (Ffile_directory_p (newname)))
-#ifdef DOS_NT
-      /* If the file names are identical but for the case,
-        don't attempt to move directory to itself. */
-      && (NILP (Fstring_equal (Fdowncase (file), Fdowncase (newname))))
-#endif
-      )
+      /* If the filesystem is case-insensitive and the file names are
+        identical but for the case, don't attempt to move directory
+        to itself.  */
+      && (NILP (Ffile_name_case_insensitive_p (file))
+         || NILP (Fstring_equal (Fdowncase (file), Fdowncase (newname)))))
     {
       Lisp_Object fname = (NILP (Ffile_directory_p (file))
                           ? file : Fdirectory_file_name (file));
@@ -2277,14 +2346,12 @@ This is what happens in interactive use with M-x.  */)
   encoded_file = ENCODE_FILE (file);
   encoded_newname = ENCODE_FILE (newname);
 
-#ifdef DOS_NT
-  /* If the file names are identical but for the case, don't ask for
-     confirmation: they simply want to change the letter-case of the
-     file name.  */
-  if (NILP (Fstring_equal (Fdowncase (file), Fdowncase (newname))))
-#endif
-  if (NILP (ok_if_already_exists)
-      || INTEGERP (ok_if_already_exists))
+  /* If the filesystem is case-insensitive and the file names are
+     identical but for the case, don't ask for confirmation: they
+     simply want to change the letter-case of the file name.  */
+  if ((!(file_name_case_insensitive_p (SSDATA (encoded_file)))
+       || NILP (Fstring_equal (Fdowncase (file), Fdowncase (newname))))
+      && ((NILP (ok_if_already_exists) || INTEGERP (ok_if_already_exists))))
     barf_or_query_if_file_exists (newname, false, "rename to it",
                                  INTEGERP (ok_if_already_exists), false);
   if (rename (SSDATA (encoded_file), SSDATA (encoded_newname)) < 0)
@@ -5836,6 +5903,7 @@ syms_of_fileio (void)
   DEFSYM (Qmake_directory_internal, "make-directory-internal");
   DEFSYM (Qmake_directory, "make-directory");
   DEFSYM (Qdelete_file, "delete-file");
+  DEFSYM (Qfile_name_case_insensitive_p, "file-name-case-insensitive-p");
   DEFSYM (Qrename_file, "rename-file");
   DEFSYM (Qadd_name_to_file, "add-name-to-file");
   DEFSYM (Qmake_symbolic_link, "make-symbolic-link");
@@ -6099,6 +6167,7 @@ This includes interactive calls to `delete-file' and
   defsubr (&Smake_directory_internal);
   defsubr (&Sdelete_directory_internal);
   defsubr (&Sdelete_file);
+  defsubr (&Sfile_name_case_insensitive_p);
   defsubr (&Srename_file);
   defsubr (&Sadd_name_to_file);
   defsubr (&Smake_symbolic_link);