[Config] CMake: Shallow clone when using the git-fetch mechanism

[fredroy]

No need to retrieve the full repository on fetching IMO

Example with BeamAdapter:

• full

git clone https://github.com/sofa-framework/BeamAdapter
...
Receiving objects: 100% (30388/30388), 44.09 MiB | 2.67 MiB/s, done.

• shallow

git clone https://github.com/sofa-framework/BeamAdapter -depth 1
...
Receiving objects: 100% (248/248), 10.09 MiB | 8.03 MiB/s, done.

Some caveats from CMake though : https://gitlab.kitware.com/cmake/cmake/-/issues/17770 , depending if GIT_TAG is a branch, a ref or... a tag (🤪)

NOTE: shallow clone does not work if GIT_TAG is hash SHA reference to a commit so I needed some cmake function to test if the argument is a hash.

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---

Reviewers will merge this pull-request only if

• it builds with SUCCESS for all platforms on the CI.
• it does not generate new warnings.
• it does not generate new unit test failures.
• it does not generate new scene test failures.
• it does not break API compatibility.
• it is more than 1 week old (or has fast-merge label).

[bakpaul]

The ci-dpends-on mechanism uses a commit hash. Could you please add a ci-depends-on to this PR to see if the cloning mechanism still works ?

[sofabot]

[ci-depends-on] detected during build #3.

To unlock the merge button, you must

• Merge or close Apply changes regarding SOFA PR 5558 BeamAdapter#197
  For this build, the following CMake flags will be set
  -DBEAMADAPTER_GIT_REPOSITORY='https://github.com/sofa-framework/BeamAdapter'
  -DBEAMADAPTER_GIT_TAG='de5305190efcb9a1bd74a87e89dddf231c90c721'

[fredroy]

The ci-dpends-on mechanism uses a commit hash. Could you please add a ci-depends-on to this PR to see if the cloning mechanism still works ?

it was already tested for commit hash, some of the dependencies of SofaImGui was using a hash for GIT_TAG (thats how I found the problem)