Better error message when target directory isn't present

[fritx]

i found that it was the directory of the dmg target path didn't exist
i think it's a little strange with that outcoming message

how about we making sure the target directory is created, using mkdirp or something? :)

[LinusU]

As I said in #63, I'm not sure that we should create the output directory.

Hmm, I'm actually not sure if it should be appdmgs responsibility to make sure that the output folder exists. I don't know of any other unix commands that does it. E.g.

$ echo 'test' > /tmp/no-exists/my-file 
zsh: no such file or directory: /tmp/no-exists/my-file

$ touch /tmp/no-exists/my-file 
touch: /tmp/no-exists/my-file: No such file or directory

$ cp linus.jpg /tmp/no-exists/my-file
cp: /tmp/no-exists/my-file: No such file or directory

$ cat test.c 
int main(void) { return 0; }
$ gcc -o /tmp/no-exists/my-file test.c 
ld: can't open output file for writing: /tmp/no-exists/my-file, errno=2 for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Now, I would like a much better error output thought. I think that the best way here is to try and create the file earlier on, and then raise helpful error if something goes wrong, and then tell hdiutil to overwrite the created empty file. This prevents ant race conditions that other approaches might have (e.g. checking if the directory exists, then starting hdiutil).

That being said, a better error message would be very appropriate.

[fritx]

oops sorry for the duplicated issue :)
entirely agreed. then how about checking the source/target before the hdiutil call?
i'm not sure it is good or not though

[LinusU]

I think that the best solution would be to start by creating target with the O_EXCL flag. That way we ensure that the file can be created; and error out early if something goes wrong.