Let `gix-testtools` use `gix-*` workspace crates

`gix-testtools` depends on several other `gix-*` crates. Before version 0.16.1 (#1972), `gix-testtools` depended on prior breaking versions of those crates (as discussed in #1510 and #1886). Since then, it depends on the current versions. When depending on a strictly earlier version, it was necessary to omit `path =` in the `gix-testtools` manifest for its `gix-*` dependencies. Now that `gix-testtools` depends on current versions of those dependencies, it seems feasible to specify both `version` and `path`, as we do in other cases where one crate developed in this workspace depends on another crate developed in the workspace. Aside from improving general consistency (which is a weak rationale here, since the role of `gix-testtools` differs substantially from that of other `gix-*` crates, in terms of how we're ourselves using it), the broad benefits here are that: 1. Ambiguity in what crate is meant, when an operation is performed on a specific `gix-*` crate, is lessened, or maybe even eliminated. (#1989) 2. Because the code of the dependency comes from the workspace when applicable, i.e. when `gix-testtools` is itself being used in the workspace, it should allow new not-yet-published functionality to be leveraged in `gix-testtools`, without confusion or breakage. (#1886) Before this, some actions we'd prefer to do by `<cmd> -p <crate>` had to be done by `(cd <crate-dir>; <cmd>)`. This was needed to operate on `gix-*` crates in the workspace that are also dependencies, even transitively, of `gix-testtools`. This affected some commands in `justfile` recipes, some commands run in CI workflows (indirectly via `just`, or directly in script steps), and some operations carried out manually. This included `cargo nextest run` and `cargo check` on various crates. Here's an example (shown on Windows, but this problem was not specific to Windows) using `gix-date`, which is not listed in `tests/tools/Cargo.toml`, but which is a transitive dependency: C:\Users\ek\source\repos\gitoxide [main ≡]> cargo nextest run -p gix-date Blocking waiting for file lock on package cache error: There are multiple `gix-date` packages in your project, and the specification `gix-date` is ambiguous. Please re-run this command with one of the following specifications: path+file:///C:/Users/ek/source/repos/gitoxide/gix-date#0.10.1 registry+https://github.com/rust-lang/crates.io-index#gix-date@0.10.1 error: command `'\\?\C:\Users\ek\.rustup\toolchains\stable-x86_64-pc-windows-msvc\bin\cargo.exe' test --no-run --message-format json-render-diagnostics --package gix-date` exited with code 101 An important special case is that of editor/IDE integration, especially in VS Code. This couldn't run and (more significantly, in view of the benefit of integration) couldn't debug some of the tests. This happened because synthesized `cargo test -p ...` commands, used behind the scenes to launch the tests, were ambiguous. For further details, see #1989. Another benefit is that the lockfile and dependency tree are simpler, and the dependency tree is truly unified. That points to an important aspect of this change, which is more than a refactoring and will affect test behavior: - It shouldn't produce different behavior when `gix-testtools` is obtained from crates.io (i.e. when projects developed outside the `gitoxide` repository use `gix-testtools`), it can produce different behavior here, where `gix-testtools` will use changes to its `gix-*` dependencies (and accordingly their own dependencies, recursively) that are present in the workspace even if not present in the released version that matches `version =`. - That could be a good thing if it causes new changes to be exercised more and earlier. That might help find bugs. - This is also desirable in that it allows feature changes and bugfixes in `gix-*` crates to be used immediately in `gix-testtools`, before either those `gix-*` crates or `gix-testtools` are published with the changes (#1886). But... However: - It could be bad if it introduces an undesirable dependency ordering for fixing bugs and/or introducing regression tests. That is, in principle there could arise two (possibly related) bugs, A and B, where there is some reason to fix A before B, but where B must be fixed in order for the regression test for A to run (to validate that it can catch A), due to B breaking `gix-testtools` as used in the test for A or in other tests in the crate affected by A. Because this would presumably be known--an error would occur, likely when building the tests--it could be worked around by temporarily (or permanently) reverting this change if and when such a problem ever arises, or partially undoing it for the specific affected `gix-*` dependency of `gix-testtools`. - It could be bad if a bug affects a `gix-*` crate and its own tests in identical or complementary ways, and this is used to establish or check an expectation. That is, in principle there could arise a bug in a `gix-*` crate that `gix-testtools` uses, and that itself uses `gix-testtools` in its tests, that causes a test that should catch that bug (either initially or to verify a bugfix) to wrongly report that the code is working. This scenario is a case of the general problem that duplicated logic between code and its tests can cause a bug to appear (either in the same form or in different forms) in both, such that tests that should catch the bug don't catch it because they suffer from the same bug. In the hypothetical case imagined here, the duplication of logic would arise from the tests calling and using the very code that is under test. For the way we are currently using or likely ever to use `gix-testtools`, it seems like this would probably not happen. But it is hard to be completely sure. Unlike the previously described scenario, if this scenario did occur, it would likely not be noticed. Both those problem scenarios have corresponding scenarios that had already applied (and which the change here at least slightly *mitigates*): if the code with the bug has already been published. This fixes #1989 and makes progress toward #1886.

EKEliah Kagan committed 1 year ago