These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.94 s (backtrack: 0/20).


The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by dev-vcs/gitg-50::gentoo
# required by =dev-vcs/gitg-50 (argument)
>=app-crypt/libsecret-0.21.8.2-r1 vala

!!! The ebuild selected to satisfy "app-crypt/libsecret[vala]" has unmet requirements.
- app-crypt/libsecret-0.21.8.2-r1::gentoo USE="crypt gcrypt pam (test-rust) -gnutls -gtk-doc -introspection -test -tpm -vala"

  The following REQUIRED_USE flag constraints are unsatisfied:
    vala? ( introspection )

  The above constraints are a subset of the following complete expression:
    vala? ( introspection ) gtk-doc? ( crypt introspection ) crypt? ( any-of ( gcrypt gnutls ) )

(dependency required by "dev-vcs/gitg-50::gentoo" [ebuild])
(dependency required by "=dev-vcs/gitg-50" [argument])