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, 3 insertions, 0 deletions

diff --git a/src/lisp.h b/src/lisp.h
index f8ffb33a641..7e7dba631f3 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4061,6 +4061,8 @@ extern void syms_of_marker (void);
 
 /* Defined in fileio.c.  */
 
+extern char *splice_dir_file (char *, char const *, char const *);
+extern char const *get_homedir (void);
 extern Lisp_Object expand_and_dir_to_file (Lisp_Object);
 extern Lisp_Object write_region (Lisp_Object, Lisp_Object, Lisp_Object,
                                  Lisp_Object, Lisp_Object, Lisp_Object,
@@ -4185,6 +4187,7 @@ extern void syms_of_frame (void);
 /* Defined in emacs.c.  */
 extern char **initial_argv;
 extern int initial_argc;
+extern char const *emacs_wd;
 #if defined (HAVE_X_WINDOWS) || defined (HAVE_NS)
 extern bool display_arg;
 #endif