Act like POSIX sh if $HOME is relative

POSIX says sh ~/foo should act like $HOME/foo even if $HOME is
relative, so be consistent with that (Bug#33255).
* admin/merge-gnulib (GNULIB_MODULES): Add dosname.
* src/buffer.c (init_buffer): Use emacs_wd to get
initial working directory with slash appended if needed.
(default-directory): Say it must be absolute.
* src/emacs.c (emacs_wd): New global variable.
(init_cmdargs): Dir arg is now char const *.
(main): Set emacs_wd.
* src/emacs.c (main) [NS_IMPL_COCOA]:
* src/fileio.c (Fexpand_file_name):
Use get_homedir instead of egetenv ("HOME").
* src/fileio.c: Include dosname.h, for IS_ABSOLUTE_FILE_NAME.
(splice_dir_file, get_homedir): New functions.
* src/xrdb.c (gethomedir): Remove.  All callers changed
to use get_homedir and splice_dir_file.
* test/src/fileio-tests.el (fileio-tests--relative-HOME): New test.

1 files changed, 8 insertions, 0 deletions

diff --git a/test/src/fileio-tests.el b/test/src/fileio-tests.el
index 5d12685fa19..b7b78bbda09 100644
--- a/test/src/fileio-tests.el
+++ b/test/src/fileio-tests.el
@@ -95,3 +95,11 @@ Also check that an encoding error can appear in a symlink."
   (should (equal (file-name-as-directory "d:/abc/") "d:/abc/"))
   (should (equal (file-name-as-directory "D:\\abc/") "d:/abc/"))
   (should (equal (file-name-as-directory "D:/abc//") "d:/abc//")))
+
+(ert-deftest fileio-tests--relative-HOME ()
+  "Test that expand-file-name works even when HOME is relative."
+  (let ((old-home (getenv "HOME")))
+    (setenv "HOME" "a/b/c")
+    (should (equal (expand-file-name "~/foo")
+                   (expand-file-name "a/b/c/foo")))
+    (setenv "HOME" old-home)))