Validate contextdir on build

We never verified that the context directory passed into the build
command was a valid directory.  When we then slapped a default Containerfile
name onto it, things went south fast if the user had passed us a file and
not a directory.

Fixes: #4383

Signed-off-by: TomSweeneyRedHat <tsweeney@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/cmd/podman/utils.go b/cmd/podman/utils.go
index c19e6391e..21389b43a 100644
--- a/cmd/podman/utils.go
+++ b/cmd/podman/utils.go
@@ -74,3 +74,13 @@ func checkIfFileExists(name string) bool {
 	}
 	return !file.IsDir()
 }
+
+// Check if a file is or is not a directory
+func fileIsDir(name string) bool {
+	file, err := os.Stat(name)
+	// All errors return file == nil
+	if err != nil {
+		return false
+	}
+	return file.IsDir()
+}