Thanks for the answer. Indeed it is working ok for FemMesh. I tested with another unregistered package called Amaru and I got the following error:
(v1.1) pkg> add https://github.com/NumSoftware/Amaru
Updating git-repo `https://github.com/NumSoftware/Amaru`
[ Info: Assigning UUID 68281456-d7ce-5e5a-b7a0-5e8bda4b7efe to Amaru
Resolving package versions...
ERROR: The following package names could not be resolved:
* DelimitedFiles (8bb1440f-4735-579b-a4ab-409b98df4dab in manifest but not in project)
* LinearAlgebra (37e2e46d-f89d-539d-b4ee-838fcccc9c8e in manifest but not in project)
* Printf (de0858da-6303-5e67-8744-51eddeeeb8d7 in manifest but not in project)
* SparseArrays (2f01184e-e22b-5df5-ae63-d93ebab69eaf in manifest but not in project)
* Test (8dfed614-e22c-5e08-85e1-65c5234f0b40 in manifest but not in project)
Please specify by known `name=uuid`.
my REQUIRE file contains:
Note that (unregistered) FemMesh is a dependency but was previously installed.
If I add manually the missing packages by
pkg> add DelimitedFiles LinearAlgebra Printf SparseArrays Test
and try again then it works.