option,main: Partial support of XDG base directory specification

- Add functions that are able to query XDG.
- Replace defaults for
  - &runtimepath. Does not follow #78.
  - &viewdir.
  - &undodir.
  - &directory.
  - &backupdir. Does not follow #78.
  - vimrc location.
- Remove user vimrc file line from :version message.

src/nvim/main.c

@@ -1840,16 +1840,9 @@ static void source_startup_scripts(mparm_T *parmp)
      * - second user exrc file ($VIM/.exrc for Dos)
      * The first that exists is used, the rest is ignored.
      */
+    char_u *user_vimrc = (char_u *)get_from_user_conf("init.vim");
     if (process_env("VIMINIT", true) != OK) {
-      if (do_source((char_u *)USR_VIMRC_FILE, TRUE, DOSO_VIMRC) == FAIL
-#ifdef USR_VIMRC_FILE2
-          && do_source((char_u *)USR_VIMRC_FILE2, TRUE,
-            DOSO_VIMRC) == FAIL
-#endif
-#ifdef USR_VIMRC_FILE3
-          && do_source((char_u *)USR_VIMRC_FILE3, TRUE,
-            DOSO_VIMRC) == FAIL
-#endif
+      if (do_source(user_vimrc, true, DOSO_VIMRC) == FAIL
           && process_env("EXINIT", FALSE) == FAIL
           && do_source((char_u *)USR_EXRC_FILE, FALSE, DOSO_NONE) == FAIL) {
 #ifdef USR_EXRC_FILE2
@@ -1875,16 +1868,8 @@ static void source_startup_scripts(mparm_T *parmp)
         secure = p_secure;
 
       i = FAIL;
-      if (path_full_compare((char_u *)USR_VIMRC_FILE,
-            (char_u *)VIMRC_FILE, FALSE) != kEqualFiles
-#ifdef USR_VIMRC_FILE2
-          && path_full_compare((char_u *)USR_VIMRC_FILE2,
-            (char_u *)VIMRC_FILE, FALSE) != kEqualFiles
-#endif
-#ifdef USR_VIMRC_FILE3
-          && path_full_compare((char_u *)USR_VIMRC_FILE3,
-            (char_u *)VIMRC_FILE, FALSE) != kEqualFiles
-#endif
+      if (path_full_compare(user_vimrc,
+            (char_u *)VIMRC_FILE, false) != kEqualFiles
 #ifdef SYS_VIMRC_FILE
           && path_full_compare((char_u *)SYS_VIMRC_FILE,
             (char_u *)VIMRC_FILE, FALSE) != kEqualFiles

src/nvim/option.c

@@ -301,6 +301,15 @@ static char *(p_cot_values[]) = {"menu", "menuone", "longest", "preview",
 # include "option.c.generated.h"
 #endif
 
+static void set_runtimepath_default(void)
+{
+  garray_T rtp_ga;
+  ga_init(&rtp_ga, (int)sizeof(const char *), 1);
+  GA_APPEND(const char *, &rtp_ga, get_user_conf_dir());
+  GA_APPEND(const char *, &rtp_ga, concat_fnames(get_user_conf_dir(), "after", true));
+  set_string_default("runtimepath", ga_concat_strings(&rtp_ga));
+}
+
 /*
  * Initialize the options, first part.
  *
@@ -437,6 +446,12 @@ void set_init_1(void)
       "system('lpr' . (&printdevice == '' ? '' : ' -P' . &printdevice) . ' ' . v:fname_in) . delete(v:fname_in) + v:shell_error"
       );
 
+  set_string_default("viewdir", (char_u *)get_from_user_data("view"));
+  set_string_default("backupdir", (char_u *)get_from_user_data("backup"));
+  set_string_default("directory", (char_u *)get_from_user_data("swap"));
+  set_string_default("undodir", (char_u *)get_from_user_data("undo"));
+  set_runtimepath_default();
+
   /*
    * Set all the options (except the terminal options) to their default
    * value.  Also set the global value for local options.

src/nvim/options.lua

@@ -176,7 +176,7 @@ return {
       vi_def=true,
       expand=true,
       varname='p_bdir',
-      defaults={if_true={vi=macros('DFLT_BDIR')}}
+      defaults={if_true={vi=''}}
     },
     {
       full_name='backupext', abbreviation='bex',
@@ -627,7 +627,7 @@ return {
       vi_def=true,
       expand=true,
       varname='p_dir',
-      defaults={if_true={vi=macros('DFLT_DIR')}}
+      defaults={if_true={vi=''}}
     },
     {
       full_name='display', abbreviation='dy',
@@ -1916,7 +1916,7 @@ return {
       vi_def=true,
       expand=true,
       varname='p_rtp',
-      defaults={if_true={vi=macros('DFLT_RUNTIMEPATH')}}
+      defaults={if_true={vi=''}}
     },
     {
       full_name='scroll', abbreviation='scr',
@@ -2524,7 +2524,7 @@ return {
       vi_def=true,
       expand=true,
       varname='p_udir',
-      defaults={if_true={vi="."}}
+      defaults={if_true={vi=''}}
     },
     {
       full_name='undofile', abbreviation='udf',
@@ -2585,7 +2585,7 @@ return {
       vi_def=true,
       expand=true,
       varname='p_vdir',
-      defaults={if_true={vi=macros('DFLT_VDIR')}}
+      defaults={if_true={vi=''}}
     },
     {
       full_name='viewoptions', abbreviation='vop',

src/nvim/os/os.h

@@ -12,6 +12,7 @@
 # include "os/mem.h.generated.h"
 # include "os/env.h.generated.h"
 # include "os/users.h.generated.h"
+# include "os/stdpaths.h.generated.h"
 #endif
 
 #endif  // NVIM_OS_OS_H

src/nvim/os/stdpaths.c

@@ -0,0 +1,100 @@
+#include "nvim/os/os.h"
+#include "nvim/strings.h"
+#include "nvim/path.h"
+#include "nvim/garray.h"
+
+typedef enum {
+  kXDGConfigHome,
+  kXDGDataHome,
+  kXDGCacheHome,
+  kXDGRuntimeDir,
+  kXDGConfigDirs,
+  kXDGDataDirs,
+} XDGDirType;
+
+static const char *xdg_env_vars[] = {
+  [kXDGConfigHome] = "XDG_CONFIG_HOME",
+  [kXDGDataHome] = "XDG_DATA_HOME",
+  [kXDGCacheHome] = "XDG_CACHE_HOME",
+  [kXDGRuntimeDir] = "XDG_RUNTIME_DIR",
+  [kXDGConfigDirs] = "XDG_CONFIG_DIRS",
+  [kXDGDataDirs] = "XDG_DATA_DIRS",
+};
+
+static const char *const xdg_defaults[] = {
+  // Windows, Apple stuff are just shims right now
+#ifdef WIN32
+  // Windows
+#elif APPLE
+  // Apple (this includes iOS, which we might need to handle differently)
+  [kXDGConfigHome] = "~/Library/Preferences",
+  [kXDGDataHome] = "~/Library/Application Support",
+  [kXDGCacheHome] = "~/Library/Caches",
+  [kXDGRuntimeDir] = "~/Library/Application Support",
+  [kXDGConfigDirs] = "/Library/Application Support",
+  [kXDGDataDirs] = "/Library/Application Support",
+#else
+  // Linux, BSD, CYGWIN
+  [kXDGConfigHome] = "~/.config",
+  [kXDGDataHome] = "~/.local/share",
+  [kXDGCacheHome] = "~/.cache",
+  [kXDGRuntimeDir] = "",
+  [kXDGConfigDirs] = "/etc/xdg/",
+  [kXDGDataDirs] = "/usr/local/share/:/usr/share/",
+};
+#endif
+
+static const char *get_xdg(XDGDirType idx)
+{
+  const char *env = xdg_env_vars[idx];
+  const char *fallback = xdg_defaults[idx];
+
+  const char *ret = os_getenv(env);
+  if (!ret && fallback) {
+    ret = (const char *)expand_env_save((char_u *)fallback);
+  }
+
+  return ret;
+}
+
+static const char *get_xdg_home(XDGDirType idx)
+{
+  const char *dir = get_xdg(idx);
+  if (dir) {
+    dir = (const char *)concat_fnames(dir, "nvim", true);
+  }
+  return dir;
+}
+
+static void create_dir(const char *dir, int mode, const char *suffix)
+{
+  char *failed;
+  if (!os_mkdir_recurse(dir, mode, &failed)) {
+    // TODO: Create a folder in $TMPDIR instead
+    DLOG("Create dir failed");
+  }
+}
+
+const char *get_user_conf_dir(void)
+{
+  return get_xdg_home(kXDGConfigHome);
+}
+
+const char *get_from_user_conf(const char * fname)
+{
+  return (const char *)concat_fnames(get_user_conf_dir(), fname, true);
+}
+
+const char *get_user_data_dir(void)
+{
+  return get_xdg_home(kXDGDataHome);
+}
+
+const char *get_from_user_data(const char * fname)
+{
+  const char *dir = (const char *)concat_fnames(get_user_data_dir(), fname, true);
+  if (!os_isdir((char_u *)dir)) {
+    create_dir(dir, 0755, fname);
+  }
+  return dir;
+}

src/nvim/os/unix_defs.h

@@ -31,12 +31,6 @@
 #ifndef USR_EXRC_FILE
 # define USR_EXRC_FILE "~/.exrc"
 #endif
-#ifndef USR_VIMRC_FILE
-# define USR_VIMRC_FILE "~/.nvimrc"
-#endif
-#ifndef USR_VIMRC_FILE2
-# define USR_VIMRC_FILE2     "~/.nvim/nvimrc"
-#endif
 #ifndef EXRC_FILE
 # define EXRC_FILE      ".exrc"
 #endif
@@ -47,27 +41,4 @@
 # define SHADA_FILE "~/.nvim/shada/main.shada"
 #endif
 
-// Default for 'backupdir'.
-#ifndef DFLT_BDIR
-# define DFLT_BDIR    ".,~/tmp,~/"
-#endif
-
-// Default for 'directory'.
-#ifndef DFLT_DIR
-# define DFLT_DIR     ".,~/tmp,/var/tmp,/tmp"
-#endif
-
-// Default for 'viewdir'.
-#ifndef DFLT_VDIR
-# define DFLT_VDIR    "~/.nvim/view"
-#endif
-
-#ifdef RUNTIME_GLOBAL
-# define DFLT_RUNTIMEPATH "~/.nvim," RUNTIME_GLOBAL ",$VIMRUNTIME," \
-  RUNTIME_GLOBAL "/after,~/.nvim/after"
-#else
-# define DFLT_RUNTIMEPATH \
-  "~/.nvim,$VIM/vimfiles,$VIMRUNTIME,$VIM/vimfiles/after,~/.nvim/after"
-#endif
-
 #endif  // NVIM_OS_UNIX_DEFS_H

src/nvim/os/win_defs.h

@@ -8,7 +8,6 @@
 
 // Defines needed to fix the build on Windows:
 // - USR_EXRC_FILE
-// - USR_VIMRC_FILE
 // - SHADA_FILE
 // - DFLT_DIR
 // - DFLT_BDIR

src/nvim/version.c

@@ -1067,21 +1067,6 @@ void list_version(void)
   version_msg(SYS_VIMRC_FILE);
   version_msg("\"\n");
 #endif  // ifdef SYS_VIMRC_FILE
-#ifdef USR_VIMRC_FILE
-  version_msg(_("     user vimrc file: \""));
-  version_msg(USR_VIMRC_FILE);
-  version_msg("\"\n");
-#endif  // ifdef USR_VIMRC_FILE
-#ifdef USR_VIMRC_FILE2
-  version_msg(_(" 2nd user vimrc file: \""));
-  version_msg(USR_VIMRC_FILE2);
-  version_msg("\"\n");
-#endif  // ifdef USR_VIMRC_FILE2
-#ifdef USR_VIMRC_FILE3
-  version_msg(_(" 3rd user vimrc file: \""));
-  version_msg(USR_VIMRC_FILE3);
-  version_msg("\"\n");
-#endif  // ifdef USR_VIMRC_FILE3
 #ifdef USR_EXRC_FILE
   version_msg(_("      user exrc file: \""));
   version_msg(USR_EXRC_FILE);