Stack clones external repositories multiple times

[jonathanknowles]

General summary

In certain situations, stack clones external dependencies multiple times instead of cloning a single time and caching the result.

In pathological cases, this causes stack to spend a great deal of time re-cloning the same repository, greatly increasing network data usage.

Steps to reproduce

1. Clone either of the following repositories:
   • minimal test case:
     https://github.com/rvl/stack-git-package-subdirs-test
   • more complex test case:
     https://github.com/input-output-hk/cardano-wallet/
2. Build with stack build --fast --test --no-run-tests --bench --no-run-benchmarks
3. Observe the build output.

Expected

Stack clones external repositories as needed, but does not clone each external repository more than once.

Actual

Stack clones certain repositories multiple times:

Stack version

$ stack --version
Version 2.5.1, Git revision d6ab861544918185236cf826cb2028abb266d6d5 x86_64 hpack-0.33.0

Method of installation

• Official binary, downloaded from stackage.org or fpcomplete's package repository

[KtorZ]

duplicate of: #5411 ?

[mpilgrem]

I am closing this issue as it appears to me also to be a duplicate of #5411.