Generated user branches can be too long

[n-raymond]

As per https://github.com/ocaml-opam/opam-publish/blob/master/src/publishSubmit.ml#L44, a generated user branch is created by concatenating each package concerned by the publication.

Publishing many packages at once can then result in creating a very long branch name / Pull Request title. This can lead to side effects depending on the file system the root directory is located, as certain file systems can't use filenames that exceed a certain size (for instance, ext4 or eCryptfs).

For example, using eCryptfs myself, I got the following error:

> opam publish "https://gitlab.com/nomadic-labs/resto/-/archive/v0.10/resto-v0.10.tar.gz" .

The following will be published:
  - resto version 0.10 with opam file at /home/pixel/Documents/Projects/NomadicLabs/resto/resto.opam
    archive at https://gitlab.com/nomadic-labs/resto/-/archive/v0.10/resto-v0.10.tar.gz
  - resto-json version 0.10 with opam file at /home/pixel/Documents/Projects/NomadicLabs/resto/resto-json.opam
    archive at https://gitlab.com/nomadic-labs/resto/-/archive/v0.10/resto-v0.10.tar.gz
  - resto-directory version 0.10 with opam file at
    /home/pixel/Documents/Projects/NomadicLabs/resto/resto-directory.opam
    archive at https://gitlab.com/nomadic-labs/resto/-/archive/v0.10/resto-v0.10.tar.gz
  - resto-cohttp version 0.10 with opam file at /home/pixel/Documents/Projects/NomadicLabs/resto/resto-cohttp.opam
    archive at https://gitlab.com/nomadic-labs/resto/-/archive/v0.10/resto-v0.10.tar.gz
  - resto-cohttp-server version 0.10 with opam file at
    /home/pixel/Documents/Projects/NomadicLabs/resto/resto-cohttp-server.opam
    archive at https://gitlab.com/nomadic-labs/resto/-/archive/v0.10/resto-v0.10.tar.gz
  - resto-cohttp-self-serving-client version 0.10 with opam file at
    /home/pixel/Documents/Projects/NomadicLabs/resto/resto-cohttp-self-serving-client.opam
    archive at https://gitlab.com/nomadic-labs/resto/-/archive/v0.10/resto-v0.10.tar.gz
  - resto-cohttp-client version 0.10 with opam file at
    /home/pixel/Documents/Projects/NomadicLabs/resto/resto-cohttp-client.opam
    archive at https://gitlab.com/nomadic-labs/resto/-/archive/v0.10/resto-v0.10.tar.gz
  - resto-acl version 0.10 with opam file at /home/pixel/Documents/Projects/NomadicLabs/resto/resto-acl.opam
    archive at https://gitlab.com/nomadic-labs/resto/-/archive/v0.10/resto-v0.10.tar.gz


You will be shown the patch before submitting.
Please confirm the above data. Continue ?  [Y/n] y
Fetching the package repository, this may take a while...
[ERROR] Uncaught exception: "/usr/bin/git fetch --multiple origin user" exited with code 1 "error: could not fetch
        user"
        
> cd ~/.opam/plugins/opam-publish/repos/ocaml%opam-repository/

> git fetch --multiple origin user
Fetching origin
Fetching user
error: cannot lock ref 'refs/remotes/user/opam-publish-resto-resto-acl-resto-cohttp-resto-cohttp-client-resto-cohttp-self-serving-client-resto-cohttp-server-resto-directory-resto-json.0.9': Unable to create '/home/pixel/.opam/plugins/opam-publish/repos/ocaml%opam-repository/.git/refs/remotes/user/opam-publish-resto-resto-acl-resto-cohttp-resto-cohttp-client-resto-cohttp-self-serving-client-resto-cohttp-server-resto-directory-resto-json.0.9.lock': File name too long
From github.com:n-raymond/opam-repository
 ! [new branch]            opam-publish-resto-resto-acl-resto-cohttp-resto-cohttp-client-resto-cohttp-self-serving-client-resto-cohttp-server-resto-directory-resto-json.0.9 -> user/opam-publish-resto-resto-acl-resto-cohttp-resto-cohttp-client-resto-cohttp-self-serving-client-resto-cohttp-server-resto-directory-resto-json.0.9  (unable to update local ref)
error: could not fetch user

It would be good to rethink this behavior to ensure branch names will not exceed a reasonable length.

[rjbou]

Completely agree, I have the same issue with opam :)

[kit-ty-kate]

#141 should fix this