cp: Add an option to visit sources in order.

This adds a --sort option which makes cp pass a comparison function to
FTS, ensuring that sources are visited and traversed in a predictable
order.  This will help make certain test cases more reliable.

Sponsored by:	Klara, Inc.
Reviewed by:	kevans
Differential Revision:	https://reviews.freebsd.org/D51214

bin/cp/cp.1

@@ -184,6 +184,18 @@ If the source file has both its set-user-ID and set-group-ID bits on,
 and either the user ID or group ID cannot be preserved, neither
 the set-user-ID nor set-group-ID bits are preserved in the copy's
 permissions.
+.It Fl -sort
+Visit and traverse sources in (non-localized) lexicographical order.
+Normally,
+.Nm
+visits the sources in the order they were listed on the command line,
+and if recursing, traverses their contents in whichever order they
+were returned in by the kernel, which may be the order in which they
+were created, lexicographical order, or something else entirely.
+With
+.Fl -sort ,
+the sources are both visited and traversed in lexicographical order.
+This is mostly useful for testing.
 .It Fl s , Fl -symbolic-link
 Create symbolic links to regular files in a hierarchy instead of copying.
 .It Fl v , Fl -verbose

bin/cp/cp.c

@@ -71,7 +71,7 @@ static char dot[] = ".";
 #define END(buf) (buf + sizeof(buf))
 PATH_T to = { .dir = -1, .end = to.path };
 bool Nflag, fflag, iflag, lflag, nflag, pflag, sflag, vflag;
-static bool Hflag, Lflag, Pflag, Rflag, rflag;
+static bool Hflag, Lflag, Pflag, Rflag, rflag, Sflag;
 volatile sig_atomic_t info;
 
 enum op { FILE_TO_FILE, FILE_TO_DIR, DIR_TO_DNE };
@@ -96,6 +96,7 @@ static const struct option long_opts[] =
 	{ "symbolic-link",	no_argument,		NULL,	's' },
 	{ "verbose",		no_argument,		NULL,	'v' },
 	{ "one-file-system",	no_argument,		NULL,	'x' },
+	{ "sort",		no_argument,		NULL,	SORT_OPT },
 	{ 0 }
 };
 
@@ -167,6 +168,9 @@ main(int argc, char *argv[])
 		case 'x':
 			fts_options |= FTS_XDEV;
 			break;
+		case SORT_OPT:
+			Sflag = true;
+			break;
 		default:
 			usage();
 		}
@@ -284,6 +288,12 @@ main(int argc, char *argv[])
 	    &to_stat)));
 }
 
+static int
+ftscmp(const FTSENT * const *a, const FTSENT * const *b)
+{
+	return (strcmp((*a)->fts_name, (*b)->fts_name));
+}
+
 static int
 copy(char *argv[], enum op type, int fts_options, struct stat *root_stat)
 {
@@ -327,7 +337,7 @@ copy(char *argv[], enum op type, int fts_options, struct stat *root_stat)
 	}
 
 	level = FTS_ROOTLEVEL;
-	if ((ftsp = fts_open(argv, fts_options, NULL)) == NULL)
+	if ((ftsp = fts_open(argv, fts_options, Sflag ? ftscmp : NULL)) == NULL)
 		err(1, "fts_open");
 	for (badcp = rval = 0;
 	     (curr = fts_read(ftsp)) != NULL;

bin/cp/tests/cp_test.sh

@@ -657,7 +657,7 @@ unrdir_body()
 	atf_check \
 	    -s exit:1 \
 	    -e match:"^cp: src/b: Permission denied" \
-	    cp -R src dst
+	    cp -R --sort src dst
 	atf_check test -d dst/a
 	atf_check cmp src/a/f dst/a/f
 	atf_check test -d dst/b
@@ -681,7 +681,7 @@ unrfile_body()
 	atf_check \
 	    -s exit:1 \
 	    -e match:"^cp: src/b: Permission denied" \
-	    cp -R src dst
+	    cp -R --sort src dst
 	atf_check test -d dst
 	atf_check cmp src/a dst/a
 	atf_check test ! -e dst/b