Can Terraform watch a directory for changes?

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In Terraform 0.12 and later, one can use a for expression combined with a fileset function and one of the hashing functions to calculate a combined checksum for files in a directory:

> sha1(join("", [for f in fileset(path.cwd, "*"): filesha1(f)]))
"77e0b2785eb7405ea5b3b610c33c3aa2dccb90ea"

The code above will calculate a sha1 checksum for each file in the current directory that matches the name pattern, join the checksums in a string and, finally, calculate a checksum for the resulting string. So the null_resource example would look like this with the expression above as a trigger:

resource "null_resource" "deploy_files" {    
  triggers = {
    dir_sha1 = sha1(join("", [for f in fileset("my-dir", "*"): filesha1(f)]))
  }

  provisioner "file" { ... }
  provisioner "remote-exec: { ... }
}

Note that fileset("my-dir", "*") does not take into account files in sub-directories of my-dir. If you want to include checksums of those use the name pattern ** instead of *.

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