Fixed Vim `mch_FullName` in os_unix.c

fix-unix_fullname.patch

diff --git a/src/Makefile b/src/Makefile
index 90b2f0c..3139102 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1926,6 +1926,7 @@ test1 \
        test_options \
        test_perl \
        test_qf_title \
+       test_resolve_swap \
        test_ruby \
        test_search_mbyte \
        test_set \
diff --git a/src/os_unix.c b/src/os_unix.c
index 8f059be..4fb9cad 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -2502,7 +2502,8 @@ mch_FullName(fname, buf, len, force)
 #endif

     /* expand it if forced or not an absolute path */
-    if (force || !mch_isFullName(fname))
+    if ((force || !mch_isFullName(fname))
+           && ((p = vim_strrchr(fname, '/')) == NULL || p != fname))
     {
        /*
         * If the file name has a path, change to that directory for a moment,
diff --git a/src/testdir/Makefile b/src/testdir/Makefile
index 39d8388..1b9c69f 100644
--- a/src/testdir/Makefile
+++ b/src/testdir/Makefile
@@ -59,6 +59,7 @@ SCRIPTS = test1.out test2.out test3.out test4.out test5.out test6.out \
                test_options.out \
                test_perl.out \
                test_qf_title.out \
+               test_resolve_swap.out \
                test_ruby.out \
                test_search_mbyte.out \
                test_set.out \
diff --git a/src/testdir/test_resolve_swap.in b/src/testdir/test_resolve_swap.in
new file mode 100644
index 0000000..9b81897
--- /dev/null
+++ b/src/testdir/test_resolve_swap.in
@@ -0,0 +1,59 @@
+Tests for swap file detection.
+This test failed, if root '/' directory not writable.
+
+STARTTEST
+:so small.vim
+:set nocompatible viminfo+=nviminfo
+:set dir=.
+:fun! TestSwap()
+:  let dir = '/'
+:  let fname = 'Xfile1'
+:  let file = dir.fname
+:  let fileswap = dir.'.'.fname.'.swp'
+:  let link = 'Xlink1'
+:  let linkswap = '.'.link.'.swp'
+:  if !filewritable(dir) || glob(file)
+:    " failed
+:    return
+:  endif
+:  call writefile([], file)
+:  exe '!ln -sfL' file link
+:  exe 'e!' link
+:  call append(0, 'test text swapfile')
+:  preserve
+:  exe '!ls' link '>>test.out'
+:  exe '!ls' linkswap '>>test.out'
+:  exe '!ls' file '>>test.out'
+:  exe '!ls' fileswap '>>test.out'
+:  set bin
+:  exe 'sp' fileswap
+:  w! /Xswap
+:  set nobin
+:  new
+:  only!
+:  exe 'bwipe!' link
+:  exe 'bwipe!' file
+:  exe 'bwipe!' fileswap
+:  call delete(linkswap)
+:  call delete(fileswap)
+:  exe '!echo start not recovered file >>test.out'
+:  exe '!cat' file '>>test.out'
+:  exe '!echo end not recovered file >>test.out'
+:  call rename('/Xswap', fileswap)
+:  exe 'recover' link
+:  w!
+:  exe '!echo start recovered file >>test.out'
+:  exe '!cat' file '>>test.out'
+:  exe '!echo end recovered file >>test.out'
+:  exe 'bwipe!' link
+:  exe 'bwipe!' file
+:  echo delete(fileswap)
+:  echo delete(linkswap)
+:  echo delete(link)
+:  echo delete(file)
+:endfun
+:call writefile([], 'test.out')
+:call TestSwap()
+:qa!
+ENDTEST
+
diff --git a/src/testdir/test_resolve_swap.ok b/src/testdir/test_resolve_swap.ok
new file mode 100644
index 0000000..d832be8
--- /dev/null
+++ b/src/testdir/test_resolve_swap.ok
@@ -0,0 +1,9 @@
+Xlink1
+/Xfile1
+/.Xfile1.swp
+start not recovered file
+end not recovered file
+start recovered file
+test text swapfile
+
+end recovered file