os_scandir: fname_case -> path_fix_case

Use os_scandir().

fname_case() only gets used when `defined(USE_FNAME_CASE)` (on operating
systems with case-insensitive file systems), but may be useful in other
contexts, so move it to path.c. (See the TODO.)

Remove the unused parameter, len.

src/nvim/buffer.c

@@ -2253,7 +2253,7 @@ setfname (
     }
     sfname = vim_strsave(sfname);
 #ifdef USE_FNAME_CASE
-    fname_case(sfname, 0);            /* set correct case for short file name */
+    path_fix_case(sfname);            /* set correct case for short file name */
 #endif
     free(buf->b_ffname);
     free(buf->b_sfname);

src/nvim/eval.c

@@ -9895,9 +9895,7 @@ static void f_has(typval_T *argvars, typval_T *rettv)
 #if defined(WIN64) || defined(_WIN64)
     "win64",
 #endif
-#ifndef CASE_INSENSITIVE_FILENAME
     "fname_case",
-#endif
 #ifdef HAVE_ACL
     "acl",
 #endif

src/nvim/ex_cmds.c

@@ -2563,7 +2563,7 @@ do_ecmd (
       sfname = ffname;
 #ifdef USE_FNAME_CASE
     if (sfname != NULL)
-      fname_case(sfname, 0);             /* set correct case for sfname */
+      path_fix_case(sfname);             // set correct case for sfname
 #endif
 
     if ((flags & ECMD_ADDBUF) && (ffname == NULL || *ffname == NUL))

src/nvim/main.c

@@ -1290,8 +1290,8 @@ scripterror:
       }
 
 #ifdef USE_FNAME_CASE
-      /* Make the case of the file name match the actual file. */
-      fname_case(p, 0);
+      // Make the case of the file name match the actual file.
+      path_fix_case(p);
 #endif
 
       alist_add(&global_alist, p,

src/nvim/os_unix.c

@@ -69,62 +69,6 @@ static int selinux_enabled = -1;
 # include "os_unix.c.generated.h"
 #endif
 
-#if defined(USE_FNAME_CASE)
-/*
- * Set the case of the file name, if it already exists.  This will cause the
- * file name to remain exactly the same.
- * Only required for file systems where case is ignored and preserved.
- */
-void fname_case(
-char_u      *name,
-int len               /* buffer size, only used when name gets longer */
-)
-{
-  char_u      *slash, *tail;
-  DIR         *dirp;
-  struct dirent *dp;
-
-  FileInfo file_info;
-  if (os_fileinfo_link((char *)name, &file_info)) {
-    /* Open the directory where the file is located. */
-    slash = vim_strrchr(name, '/');
-    if (slash == NULL) {
-      dirp = opendir(".");
-      tail = name;
-    } else {
-      *slash = NUL;
-      dirp = opendir((char *)name);
-      *slash = '/';
-      tail = slash + 1;
-    }
-
-    if (dirp != NULL) {
-      while ((dp = readdir(dirp)) != NULL) {
-        /* Only accept names that differ in case and are the same byte
-         * length. TODO: accept different length name. */
-        if (STRICMP(tail, dp->d_name) == 0
-            && STRLEN(tail) == STRLEN(dp->d_name)) {
-          char_u newname[MAXPATHL + 1];
-
-          /* Verify the inode is equal. */
-          STRLCPY(newname, name, MAXPATHL + 1);
-          STRLCPY(newname + (tail - name), dp->d_name,
-              MAXPATHL - (tail - name) + 1);
-          FileInfo file_info_new;
-          if (os_fileinfo_link((char *)newname, &file_info_new)
-              && os_fileinfo_id_equal(&file_info, &file_info_new)) {
-            STRCPY(tail, dp->d_name);
-            break;
-          }
-        }
-      }
-
-      closedir(dirp);
-    }
-  }
-}
-#endif
-
 #if defined(HAVE_ACL)
 # ifdef HAVE_SYS_ACL_H
 #  include <sys/acl.h>

src/nvim/path.c

@@ -1617,13 +1617,68 @@ char_u *fix_fname(char_u *fname)
   fname = vim_strsave(fname);
 
 # ifdef USE_FNAME_CASE
-  fname_case(fname, 0);  // set correct case for file name
+  path_fix_case(fname);  // set correct case for file name
 # endif
 
   return fname;
 #endif
 }
 
+/// Set the case of the file name, if it already exists.  This will cause the
+/// file name to remain exactly the same.
+/// Only required for file systems where case is ignored and preserved.
+// TODO(SplinterOfChaos): Could also be used when mounting case-insensitive
+// file systems.
+void path_fix_case(char_u *name)
+  FUNC_ATTR_NONNULL_ALL
+{
+  FileInfo file_info;
+  if (!os_fileinfo_link((char *)name, &file_info)) {
+    return;
+  }
+
+  // Open the directory where the file is located.
+  char_u *slash = vim_strrchr(name, '/');
+  char_u *tail;
+  Directory dir;
+  bool ok;
+  if (slash == NULL) {
+    ok = os_scandir(&dir, ".");
+    tail = name;
+  } else {
+    *slash = NUL;
+    ok = os_scandir(&dir, (char *) name);
+    *slash = '/';
+    tail = slash + 1;
+  }
+
+  if (!ok) {
+    return;
+  }
+
+  char_u *entry;
+  while ((entry = (char_u *) os_scandir_next(&dir))) {
+    // Only accept names that differ in case and are the same byte
+    // length. TODO: accept different length name.
+    if (STRICMP(tail, entry) == 0 && STRLEN(tail) == STRLEN(entry)) {
+      char_u newname[MAXPATHL + 1];
+
+      // Verify the inode is equal.
+      STRLCPY(newname, name, MAXPATHL + 1);
+      STRLCPY(newname + (tail - name), entry,
+              MAXPATHL - (tail - name) + 1);
+      FileInfo file_info_new;
+      if (os_fileinfo_link((char *)newname, &file_info_new)
+          && os_fileinfo_id_equal(&file_info, &file_info_new)) {
+        STRCPY(tail, entry);
+        break;
+      }
+    }
+  }
+
+  os_closedir(&dir);
+}
+
 /*
  * Return TRUE if "p" points to just after a path separator.
  * Takes care of multi-byte characters.