Allow file reading in the middle of request body

[cww0614]

IMHO the regular expression to match the pattern is strict enough that in few cases will this collide with real body contents, and this enables more intuitive body construction, especially when uploading files with multipart/form-data. Futhermore, this should also allow variable substitution in file paths.

[arichiardi]

LGTM! And nice 😄

[arichiardi]

I tried this in my branch but it does not seem to work. The error I see is a cryptic Args out of range: 62, 66. The regex does find the file and tries to replace things. It is basically replace-regexp-in-string that seems to fail.

[cww0614]

I tried this in my branch but it does not seem to work. The error I see is a cryptic Args out of range: 62, 66. The regex does find the file and tries to replace things. It is basically replace-regexp-in-string that seems to fail.

Can you give an example that will cause this?