fix(cmake): don't use GIT_SHALLOW when a dependency is pinned to a commit

[predat]

Problem

av_add_cmake_dep (in src/cmake/Helpers.cmake) enabled GIT_SHALLOW TRUE
for every git dependency.

A shallow clone (git clone --depth 1) only fetches the tip of the remote's
default branch. When GIT_TAG is a commit hash that is not that tip, the
subsequent checkout fails:

fatal: unable to read tree <sha>
CMake Error: Failed to checkout tag: '<sha>'

The commit is not actually missing — it is fetchable — but the shallow clone
never downloads it, so the checkout cannot find it.

Impact

This breaks ALICEVISION_BUILD_DEPENDENCIES for any dependency pinned to a
commit that is not the default-branch tip. Concretely, the dependency build
fails on popsift and cctag. Dependencies pinned to a hash that happens
to be the default-branch tip only built by luck.

Dependencies referenced by a named branch/tag (v4.5.1, main, …) are
unaffected.

Fix

Enable GIT_SHALLOW only when GIT_TAG is a named branch/tag, not a raw
commit hash:

if(NOT _D_GIT_TAG MATCHES "^[0-9a-fA-F]+$")
    list(APPEND _D_SRC_ARGS GIT_SHALLOW TRUE)
endif()

• Named refs keep the shallow-clone speedup.
• Commit-pinned deps get a full clone and check out reliably.

Notes

Regression introduced in 634581fb4 ("modernize Docker/CMake infrastructure"),
which added the unconditional GIT_SHALLOW TRUE.

Verified by a full ALICEVISION_BUILD_DEPENDENCIES Docker build (Rocky 9 +
CUDA 12.1.1): with this change, popsift and cctag clone and build correctly,
and the whole dependency set builds to completion.

[gemini-code-assist]

Code Review

This pull request updates the CMake helper macro to conditionally enable shallow cloning only when the Git tag is not a commit hash, avoiding checkout failures. The feedback recommends quoting the variable in the CMake conditional check to prevent syntax errors if the variable is empty or contains special characters.

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[gemini-code-assist]

In CMake, it is highly recommended to quote variables in if conditions when using MATCHES. If _D_GIT_TAG is empty, undefined, or contains special characters (such as spaces, semicolons, or parentheses), an unquoted variable expansion can lead to syntax errors or unexpected behavior during the CMake configuration step. Quoting it as "${_D_GIT_TAG}" ensures it is always safely evaluated as a single string.

        if(NOT "${_D_GIT_TAG}" MATCHES "^[0-9a-fA-F]+$")

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud