Add %{exists:...} builtin macro for testing file existence

doc/manual/macros.md

@@ -80,6 +80,7 @@ to perform useful operations. The current list is
 
 	%{basename:...}	basename(1) macro analogue
 	%{dirname:...}	dirname(1) macro analogue
+	%{exists:...}	test file existence, expands to 1/0
 	%{suffix:...}	expand to suffix part of a file name
 	%{url2path:...}	convert url to a local path
 	%{getenv:...}	getenv(3) macro analogue

rpmio/macro.c

@@ -625,6 +625,7 @@ static struct builtins_s {
     { "dump", 		doDump,		ME_PARSE },
     { "echo",		doOutput,	ME_ARGFUNC },
     { "error",		doOutput,	ME_ARGFUNC },
+    { "exists",		doFoo,		ME_ARGFUNC },
     { "expand",		doExpand,	ME_ARGFUNC },
     { "expr",		doFoo,		ME_ARGFUNC },
     { "getconfdir",	doFoo,		ME_FUNC },
@@ -1285,6 +1286,8 @@ doFoo(MacroBuf mb, int chkexist, int negate, rpmMacroEntry me,
     } else if (rstreq("getncpus", me->name)) {
 	sprintf(buf, "%u", getncpus());
 	b = buf;
+    } else if (rstreq("exists", me->name)) {
+	b = (access(buf, F_OK) == 0) ? "1" : "0";
     }
 
     if (b) {

tests/rpmmacro.at

@@ -782,6 +782,22 @@ runroot rpm --eval '%{verbose:zzz}'
 ])
 AT_CLEANUP
 
+AT_SETUP([%exists macro])
+AT_KEYWORDS([macros])
+AT_CHECK([
+runroot rpm \
+	--eval "%{exists:/data}" \
+	--eval "%{exists:/zzz}" \
+	--eval "%{exists}"
+],
+[1],
+[1
+0
+],
+[error: %exists: argument expected
+])
+AT_CLEANUP
+
 AT_SETUP([macro with a line starting by "{"])
 AT_KEYWORDS([macros])
 AT_CHECK([