failed to compile cargo-dinghy v0.3.2 - multiple packages link to native library git2

[Marc Trey]

with rustc 1.27.0-beta.6 (60d8c667f 2018-05-21)

error: failed to compile `cargo-dinghy v0.3.2`, intermediate artifacts can be found at `/tmp/cargo-installJC5Rne`

Caused by:
  multiple packages link to native library `git2`, but a native library can be linked only once

package `libgit2-sys v0.6.19`
    ... which is depended on by `cargo v0.24.0`
    ... which is depended on by `cargo-dinghy v0.3.2`
links to native library `git2`

package `libgit2-sys v0.7.1`
    ... which is depended on by `git2 v0.7.1`
    ... which is depended on by `git2-curl v0.8.1`
    ... which is depended on by `cargo v0.27.0`
    ... which is depended on by `dinghy-lib v0.3.4`
    ... which is depended on by `cargo-dinghy v0.3.2`
also links to native library `git2`

[Thibaut Lorrain]

we do not depends on libgit2-sys anymore since #157