remove cargo fetch calls

Summary:
Currently, the open source build contains this line in a `Cargo.toml` file:

https://github.com/facebook/sapling-staging/blob/c403b32adb27eb0c2d8a6a63261b9bf8942138ca/eden/scm/Cargo.toml#L7

For posterity, the contents of the line are:

```
graphql-parser = { git = "https://github.com/vmagro/graphql-parser", rev = "1d155d96e6052767380ab5e67c57e3d6608a31ac" }
```

The `cargo fetch` calls I am removing in this diff *used to* work. But today when
I ran the workflow that used this `Dockerfile`, they failed with:

```
#13 4.589 error: failed to resolve patches for `https://github.com/rust-lang/crates.io-index`
#13 4.589
#13 4.589 Caused by:
#13 4.589   failed to load source for dependency `graphql-parser`
#13 4.589
#13 4.589 Caused by:
#13 4.589   Unable to update https://github.com/vmagro/graphql-parser?rev=1d155d96e6052767380ab5e67c57e3d6608a31ac
#13 4.589
#13 4.589 Caused by:
#13 4.589   revspec '1d155d96e6052767380ab5e67c57e3d6608a31ac' not found; class=Reference (4); code=NotFound (-3)
#13 ERROR: process "/bin/sh -c cargo fetch --manifest-path eden/scm/exec/hgmain/Cargo.toml" did not complete successfully: exit code: 101
------
 > [ 8/17] RUN cargo fetch --manifest-path eden/scm/exec/hgmain/Cargo.toml:
#13 4.589 error: failed to resolve patches for `https://github.com/rust-lang/crates.io-index`
#13 4.589
#13 4.589 Caused by:
#13 4.589   failed to load source for dependency `graphql-parser`
#13 4.589
#13 4.589 Caused by:
#13 4.589   Unable to update https://github.com/vmagro/graphql-parser?rev=1d155d96e6052767380ab5e67c57e3d6608a31ac
#13 4.589
#13 4.589 Caused by:
#13 4.589   revspec '1d155d96e6052767380ab5e67c57e3d6608a31ac' not found; class=Reference (4); code=NotFound (-3)
```

What happened? Here's what it looks like:

- After discovering that our `Cargo.toml` files created by `autocargo` contained massive
  `[patch.crates-io]` sections that appeared to be slowing down our open source build,
  I went and posted about it in the Source Control Team group:
  https://fb.workplace.com/groups/sourcecontrolteam/posts/5310340079087295
- One way to improve the situation is to eliminate these patches from `//third-party/rust`,
  so I spot-checked a number of the patches, tracking down the diff that introduced them,
  and attempted to follow-up with the author to upstream the patch.
- D37532244 (199330f) appeared to be the diff that pulled in the patch for `graphql-parser`.
  In the comments, I pinged the author (vmagro) to see if he could upstream his patch.
- Vinnie agreed and updated his PR: graphql-rust/graphql-parser#66
- *what appears to have happened* is that Vinnie updated the PR by doing a "force push"
  where the previous head was `1d155d96e6052767380ab5e67c57e3d6608a31ac` and
  the new head is `c778917f57f6b2c26d9291819b9bb341a2f5948a`.
- GitHub...does not like force pushes. Indeed, if you visit
  graphql-rust/graphql-parser@1d155d9
  you see a yellow warning banner at the top that says
  **This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.**

I don't know what call `cargo` makes to resolve these `git` dependencies, but I assume
GitHub is refusing to respond as it normally would for orphaned commits such as these.

D39190591 (f500204) is the for fbsource overall, but based on this experience, I still think it is best
to remove these `cargo fetch` calls. Of note, **even though the `cargo fetch` calls failed,
the GitHub action to build Sapling still succeeds** because Sapling does not depend
on `graphql-parser`, so `cargo build` only builds what it needs whereas `cargo fetch`
fetches everything in the `Cargo.toml` whether it needs it or not.

In sum, given the current state of `autocargo` and the `[patch.crates-io]` section it generates,
`cargo fetch` just seems like a giant liability, so we are better off without it.

Reviewed By: fanzeyi

Differential Revision: D39189595

fbshipit-source-id: cbdf3c51e39b7ed2e49a4373e7f9fc66337766cc

Author: bolinfest

ci/gen_workflows.py

@@ -13,13 +13,6 @@
 
 DOCKERFILE_DIR = ".github/workflows"
 
-CARGO_FETCH_PATHS = [
-    "eden/scm/exec/hgmain/Cargo.toml",
-    "eden/scm/edenscmnative/conch_parser/Cargo.toml",
-    "eden/scm/exec/scratch/Cargo.toml",
-    "eden/scm/exec/scm_daemon/Cargo.toml",
-]
-
 UBUNTU_VERSIONS = ["20.04", "22.04"]
 
 UBUNTU_VERSION_DEPS = {
@@ -80,15 +73,6 @@ def __init__(self, out_dir: Path):
     def gen_build_ubuntu_image(self, *, ubuntu_version: str) -> None:
         image_name = f"ubuntu:{ubuntu_version}"
         dockerfile_name = f"sapling-cli-ubuntu-{ubuntu_version}.Dockerfile"
-        cargo_prefetch_commands = "".join(
-            [f"RUN cargo fetch --manifest-path {p}\n" for p in CARGO_FETCH_PATHS]
-        )
-        if cargo_prefetch_commands:
-            cargo_prefetch_commands = (
-                "\n# Run `cargo fetch` on the crates we plan to build.\n"
-                + cargo_prefetch_commands
-            )
-
         full_deps = UBUNTU_DEPS + UBUNTU_VERSION_DEPS[ubuntu_version]
         dockerfile = f"""\
 FROM {image_name}
@@ -113,7 +97,7 @@ def gen_build_ubuntu_image(self, *, ubuntu_version: str) -> None:
 # so assume it needs everything.
 COPY . /tmp/repo
 WORKDIR /tmp/repo
-{cargo_prefetch_commands}
+
 # Create and populate a Yarn offline mirror by running `yarn install`
 # in the addons/ folder that contains yarn.lock, package.json, and the
 # package.json file for each entry in the Yarn workspace.