Error rendering/uploading documentation on Travis

[killercup]

In #556 I noticed that travis-cargo apparently does not like generating/uploading documentation from a Cargo workspace.

The current script on master is:

 if [[ "$TRAVIS_RUST_VERSION" == stable ]]; then
      (cd diesel && travis-cargo doc -- --features "postgres sqlite chrono uuid")
      (echo "docs.diesel.rs" > diesel/target/doc/CNAME)
      (cd diesel && travis-cargo doc-upload)
    fi

which errors with:

/home/travis/build.sh: line 59: diesel/target/doc/CNAME: No such file or directory
uploading docs...
Traceback (most recent call last):
  File "/home/travis/.local/bin/travis-cargo", line 11, in <module>
    sys.exit(main())
  File "/home/travis/.local/lib/python2.7/site-packages/travis_cargo.py", line 434, in main
    args.func(version, manifest, args)
  File "/home/travis/.local/lib/python2.7/site-packages/travis_cargo.py", line 144, in doc_upload
    with open('target/doc/index.html', 'w') as f:
IOError: [Errno 2] No such file or directory: 'target/doc/index.html'

---

In #556 I changed this to not do cd diesel before doc-upload, i.e., the script is:

if [[ "$TRAVIS_RUST_VERSION" == stable ]] && [[ "$TRAVIS_BRANCH" == master ]]; then
      (cd diesel && travis-cargo doc -- --features "postgres sqlite chrono uuid")
      (echo "docs.diesel.rs" > target/doc/CNAME)
      (travis-cargo doc-upload)
    fi

but this errors with:

Cargo failed to read `--manifest-path /home/travis/build/diesel-rs/diesel/Cargo.toml` and `--manifest-path /home/travis/build/diesel-rs/diesel`:
error: found a virtual manifest at `/home/travis/build/diesel-rs/diesel/Cargo.toml` instead of a package manifest
error: the manifest-path must be a path to a Cargo.toml file