stat: add %m to output the mount point for a file

* src/find-mount-point.c: A new file refactoring
find_mount_point() out from df.c
* src/find-mount-point.h: Likewise.
* src/df.c: Use the new find-mount-point module.
* src/stat.c (print_stat): Handle the new %m format.
(find_bind_mount): A new function to
return the bind mount for a file if any.
(out_mount_mount): Print the bind mount for a file, or else
the standard mount point given by the find-mount-point module.
(usage): Document the %m format directive.
* src/Makefile.am: Reference the refactored find-mount-point.c
* po/POTFILES.in: Add find_mount_point.c to the translation list
* doc/coreutils.texi (stat invocation): Document %m,
and how it may differ from the mount point that df outputs.
* test/misc/stat-mount: A new test to correlate mount points
output from df and stat.
* tests/Makefile.am: Reference the new test.
* NEWS: Mention the new feature
* THANKS: Add the author

Signed-off-by: Pádraig Brady <P@draigBrady.com>

1 files changed, 1 insertions, 90 deletions

diff --git a/src/df.c b/src/df.c
index 24877ab13..749ce1a12 100644
--- a/src/df.c
+++ b/src/df.c
@@ -29,8 +29,7 @@
 #include "human.h"
 #include "mountlist.h"
 #include "quote.h"
-#include "save-cwd.h"
-#include "xgetcwd.h"
+#include "find-mount-point.h"
 
 /* The official name of this program (e.g., no `g' prefix).  */
 #define PROGRAM_NAME "df"
@@ -522,94 +521,6 @@ show_dev (char const *disk, char const *mount_point,
   putchar ('\n');
 }
 
-/* Return the root mountpoint of the file system on which FILE exists, in
-   malloced storage.  FILE_STAT should be the result of stating FILE.
-   Give a diagnostic and return NULL if unable to determine the mount point.
-   Exit if unable to restore current working directory.  */
-static char *
-find_mount_point (const char *file, const struct stat *file_stat)
-{
-  struct saved_cwd cwd;
-  struct stat last_stat;
-  char *mp = NULL;		/* The malloced mount point.  */
-
-  if (save_cwd (&cwd) != 0)
-    {
-      error (0, errno, _("cannot get current directory"));
-      return NULL;
-    }
-
-  if (S_ISDIR (file_stat->st_mode))
-    /* FILE is a directory, so just chdir there directly.  */
-    {
-      last_stat = *file_stat;
-      if (chdir (file) < 0)
-        {
-          error (0, errno, _("cannot change to directory %s"), quote (file));
-          return NULL;
-        }
-    }
-  else
-    /* FILE is some other kind of file; use its directory.  */
-    {
-      char *xdir = dir_name (file);
-      char *dir;
-      ASSIGN_STRDUPA (dir, xdir);
-      free (xdir);
-
-      if (chdir (dir) < 0)
-        {
-          error (0, errno, _("cannot change to directory %s"), quote (dir));
-          return NULL;
-        }
-
-      if (stat (".", &last_stat) < 0)
-        {
-          error (0, errno, _("cannot stat current directory (now %s)"),
-                 quote (dir));
-          goto done;
-        }
-    }
-
-  /* Now walk up FILE's parents until we find another file system or /,
-     chdiring as we go.  LAST_STAT holds stat information for the last place
-     we visited.  */
-  while (true)
-    {
-      struct stat st;
-      if (stat ("..", &st) < 0)
-        {
-          error (0, errno, _("cannot stat %s"), quote (".."));
-          goto done;
-        }
-      if (st.st_dev != last_stat.st_dev || st.st_ino == last_stat.st_ino)
-        /* cwd is the mount point.  */
-        break;
-      if (chdir ("..") < 0)
-        {
-          error (0, errno, _("cannot change to directory %s"), quote (".."));
-          goto done;
-        }
-      last_stat = st;
-    }
-
-  /* Finally reached a mount point, see what it's called.  */
-  mp = xgetcwd ();
-
-done:
-  /* Restore the original cwd.  */
-  {
-    int save_errno = errno;
-    if (restore_cwd (&cwd) != 0)
-      error (EXIT_FAILURE, errno,
-             _("failed to return to initial working directory"));
-    free_cwd (&cwd);
-    errno = save_errno;
-  }
-
-  return mp;
-}
-
 /* If DISK corresponds to a mount point, show its usage
    and return true.  Otherwise, return false.  */
 static bool