vim-patch:8.1.0251: support full paths for 'backupdir' #11269

Problem:    Using a full path is supported for 'directory' but not for
            'backupdir'. (Mikolaj Machowski)
Solution:   Support 'backupdir' as well. (Christian Brabandt, closes vim/vim#179)
b782ba475a

runtime/doc/options.txt

@@ -843,6 +843,14 @@ A jump table for the options with a short description can be found at |Q_op|.
 	  name, precede it with a backslash.
 	- To include a comma in a directory name precede it with a backslash.
 	- A directory name may end in an '/'.
+	- For Unix and Win32, if a directory ends in two path separators "//",
+	  the swap file name will be built from the complete path to the file
+	  with all path separators changed to percent '%' signs. This will
+	  ensure file name uniqueness in the backup directory.
+	  On Win32, it is also possible to end with "\\".  However, When a
+	  separating comma is following, you must use "//", since "\\" will
+	  include the comma in the file name. Therefore it is recommended to
+	  use '//', instead of '\\'.
 	- Environment variables are expanded |:set_env|.
 	- Careful with '\' characters, type one before a space, type two to
 	  get one in the option (see |option-backslash|), for example: >
@@ -1992,12 +2000,14 @@ A jump table for the options with a short description can be found at |Q_op|.
 	- A directory starting with "./" (or ".\" for Windows) means to
 	  put the swap file relative to where the edited file is.  The leading
 	  "." is replaced with the path name of the edited file.
-	- For Unix and Win32, if a directory ends in two path separators "//"
-	  or "\\", the swap file name will be built from the complete path to
-	  the file with all path separators substituted to percent '%' signs.
-	  This will ensure file name uniqueness in the preserve directory.
-	  On Win32, when a separating comma is following, you must use "//",
-	  since "\\" will include the comma in the file name.
+	- For Unix and Win32, if a directory ends in two path separators "//",
+	  the swap file name will be built from the complete path to the file
+	  with all path separators substituted to percent '%' signs. This will
+	  ensure file name uniqueness in the preserve directory.
+	  On Win32, it is also possible to end with "\\".  However, When a
+	  separating comma is following, you must use "//", since "\\" will
+	  include the comma in the file name. Therefore it is recommended to
+	  use '//', instead of '\\'.
 	- Spaces after the comma are ignored, other spaces are considered part
 	  of the directory name.  To have a space at the start of a directory
 	  name, precede it with a backslash.

src/nvim/fileio.c

@@ -2650,6 +2650,7 @@ buf_write(
    */
   if (!(append && *p_pm == NUL) && !filtering && perm >= 0 && dobackup) {
     FileInfo file_info;
+    const bool no_prepend_dot = false;
 
     if ((bkc & BKC_YES) || append) {       /* "yes" */
       backup_copy = TRUE;
@@ -2737,6 +2738,7 @@ buf_write(
       int some_error = false;
       char_u      *dirp;
       char_u      *rootname;
+      char_u      *p;
 
       /*
        * Try to make the backup in each directory in the 'bdir' option.
@@ -2756,6 +2758,17 @@ buf_write(
          * Isolate one directory name, using an entry in 'bdir'.
          */
         (void)copy_option_part(&dirp, IObuff, IOSIZE, ",");
+        p = IObuff + STRLEN(IObuff);
+        if (after_pathsep((char *)IObuff, (char *)p) && p[-1] == p[-2]) {
+          // Ends with '//', Use Full path
+          if ((p = (char_u *)make_percent_swname((char *)IObuff, (char *)fname))
+              != NULL) {
+            backup = (char_u *)modname((char *)p, (char *)backup_ext,
+                                       no_prepend_dot);
+            xfree(p);
+          }
+        }
+
         rootname = get_file_in_dir(fname, IObuff);
         if (rootname == NULL) {
           some_error = TRUE;                /* out of memory */
@@ -2764,10 +2777,14 @@ buf_write(
 
         FileInfo file_info_new;
         {
-          /*
-           * Make backup file name.
-           */
-          backup = (char_u *)modname((char *)rootname, (char *)backup_ext, FALSE);
+          //
+          // Make the backup file name.
+          //
+          if (backup == NULL) {
+            backup = (char_u *)modname((char *)rootname, (char *)backup_ext,
+                                       no_prepend_dot);
+          }
+
           if (backup == NULL) {
             xfree(rootname);
             some_error = TRUE;                          /* out of memory */
@@ -2893,12 +2910,26 @@ nobackup:
          * Isolate one directory name and make the backup file name.
          */
         (void)copy_option_part(&dirp, IObuff, IOSIZE, ",");
-        rootname = get_file_in_dir(fname, IObuff);
-        if (rootname == NULL)
-          backup = NULL;
-        else {
-          backup = (char_u *)modname((char *)rootname, (char *)backup_ext, FALSE);
-          xfree(rootname);
+        p = IObuff + STRLEN(IObuff);
+        if (after_pathsep((char *)IObuff, (char *)p) && p[-1] == p[-2]) {
+          // path ends with '//', use full path
+          if ((p = (char_u *)make_percent_swname((char *)IObuff, (char *)fname))
+              != NULL) {
+            backup = (char_u *)modname((char *)p, (char *)backup_ext,
+                                       no_prepend_dot);
+            xfree(p);
+          }
+        }
+
+        if (backup == NULL) {
+          rootname = get_file_in_dir(fname, IObuff);
+          if (rootname == NULL) {
+            backup = NULL;
+          } else {
+            backup = (char_u *)modname((char *)rootname, (char *)backup_ext,
+                                       no_prepend_dot);
+            xfree(rootname);
+          }
         }
 
         if (backup != NULL) {

src/nvim/memline.c

@@ -1437,7 +1437,7 @@ recover_names (
  * Append the full path to name with path separators made into percent
  * signs, to dir. An unnamed buffer is handled as "" (<currentdir>/"")
  */
-static char *make_percent_swname(const char *dir, char *name)
+char *make_percent_swname(const char *dir, char *name)
   FUNC_ATTR_NONNULL_ARG(1)
 {
   char *d = NULL;

src/nvim/testdir/test_alot.vim

@@ -2,6 +2,7 @@
 " This makes testing go faster, since Vim doesn't need to restart.
 
 source test_assign.vim
+source test_backup.vim
 source test_behave.vim
 source test_cd.vim
 source test_changedtick.vim

src/nvim/testdir/test_backup.vim

@@ -0,0 +1,58 @@
+" Tests for the backup function
+
+func Test_backup()
+  set backup backupdir=.
+  new
+  call setline(1, ['line1', 'line2'])
+  :f Xbackup.txt
+  :w! Xbackup.txt
+  " backup file is only created after
+  " writing a second time (before overwriting)
+  :w! Xbackup.txt
+  let l = readfile('Xbackup.txt~')
+  call assert_equal(['line1', 'line2'], l)
+  bw!
+  set backup&vim backupdir&vim
+  call delete('Xbackup.txt')
+  call delete('Xbackup.txt~')
+endfunc
+
+func Test_backup2()
+  set backup backupdir=.//
+  new
+  call setline(1, ['line1', 'line2', 'line3'])
+  :f Xbackup.txt
+  :w! Xbackup.txt
+  " backup file is only created after
+  " writing a second time (before overwriting)
+  :w! Xbackup.txt
+  sp *Xbackup.txt~
+  call assert_equal(['line1', 'line2', 'line3'], getline(1,'$'))
+  let f=expand('%')
+  call assert_match('src%nvim%testdir%Xbackup.txt\~', f)
+  bw!
+  bw!
+  call delete('Xbackup.txt')
+  call delete(f)
+  set backup&vim backupdir&vim
+endfunc
+
+func Test_backup2_backupcopy()
+  set backup backupdir=.// backupcopy=yes
+  new
+  call setline(1, ['line1', 'line2', 'line3'])
+  :f Xbackup.txt
+  :w! Xbackup.txt
+  " backup file is only created after
+  " writing a second time (before overwriting)
+  :w! Xbackup.txt
+  sp *Xbackup.txt~
+  call assert_equal(['line1', 'line2', 'line3'], getline(1,'$'))
+  let f=expand('%')
+  call assert_match('src%nvim%testdir%Xbackup.txt\~', f)
+  bw!
+  bw!
+  call delete('Xbackup.txt')
+  call delete(f)
+  set backup&vim backupdir&vim backupcopy&vim
+endfunc

test/functional/core/fileio_spec.lua

@@ -9,9 +9,12 @@ local nvim_prog = helpers.nvim_prog
 local request = helpers.request
 local retry = helpers.retry
 local rmdir = helpers.rmdir
+local mkdir = helpers.mkdir
 local sleep = helpers.sleep
 local read_file = helpers.read_file
 local trim = helpers.trim
+local currentdir = helpers.funcs.getcwd
+local iswin = helpers.iswin
 
 describe('fileio', function()
   before_each(function()
@@ -24,6 +27,7 @@ describe('fileio', function()
     os.remove('Xtest_startup_file2')
     os.remove('Xtest_тест.md')
     rmdir('Xtest_startup_swapdir')
+    rmdir('Xtest_backupdir')
   end)
 
   it('fsync() codepaths #8304', function()
@@ -88,6 +92,27 @@ describe('fileio', function()
     eq('foo', bar_contents);
   end)
 
+  it('backup with full path #11214', function()
+    clear()
+    mkdir('Xtest_backupdir')
+    command('set backup')
+    command('set backupdir=Xtest_backupdir//')
+    command('write Xtest_startup_file1')
+    feed('ifoo<esc>')
+    command('write')
+    feed('Abar<esc>')
+    command('write')
+
+    -- Backup filename = fullpath, separators replaced with "%".
+    local backup_file_name = string.gsub(currentdir()..'/Xtest_startup_file1',
+      iswin() and '[:/\\]' or '/', '%%') .. '~'
+    local foo_contents = trim(read_file('Xtest_backupdir/'..backup_file_name))
+    local foobar_contents = trim(read_file('Xtest_startup_file1'))
+
+    eq('foobar', foobar_contents);
+    eq('foo', foo_contents);
+  end)
+
   it('readfile() on multibyte filename #10586', function()
     clear()
     local text = {