refactor(build): improve err when file specified by -f does not exist

When the user specifies a Containerfile or Dockfile with the -f flag in podman build, if the file does not exist, the error should be intuitive to the user.

Fixed: containers#22940

Signed-off-by: Kevin Cui <bh@bugs.cc>

cmd/podman/common/build.go

@@ -202,10 +202,7 @@ func ParseBuildOpts(cmd *cobra.Command, args []string, buildOpts *BuildFlagsWrap
 		// No context directory or URL was specified.  Try to use the home of
 		// the first locally-available Containerfile.
 		for i := range containerFiles {
-			if strings.HasPrefix(containerFiles[i], "http://") ||
-				strings.HasPrefix(containerFiles[i], "https://") ||
-				strings.HasPrefix(containerFiles[i], "git://") ||
-				strings.HasPrefix(containerFiles[i], "github.com/") {
+			if isUrl(containerFiles[i]) {
 				continue
 			}
 			absFile, err := filepath.Abs(containerFiles[i])
@@ -239,6 +236,16 @@ func ParseBuildOpts(cmd *cobra.Command, args []string, buildOpts *BuildFlagsWrap
 		default:
 			return nil, fmt.Errorf("no Containerfile or Dockerfile specified or found in context directory, %s: %w", contextDir, syscall.ENOENT)
 		}
+	} else {
+		for _, f := range containerFiles {
+			if isUrl(f) || f == "/dev/stdin" {
+				continue
+			}
+			if !utils.FileExists(f) {
+				return nil, fmt.Errorf("the specified Containerfile or Dockerfile does not exist, %s: %w", f, syscall.ENOENT)
+			}
+		}
+
 	}
 
 	var logFile *os.File
@@ -628,3 +635,10 @@ func parseDockerignore(ignoreFile string) ([]string, error) {
 	}
 	return excludes, nil
 }
+
+func isUrl(s string) bool {
+	return strings.HasPrefix(s, "http://") ||
+		strings.HasPrefix(s, "https://") ||
+		strings.HasPrefix(s, "git://") ||
+		strings.HasPrefix(s, "github.com/")
+}