diff --git a/tools/go/BUILD b/tools/go/BUILD
index 25b3adb..2c251a0 100644
--- a/tools/go/BUILD
+++ b/tools/go/BUILD
@@ -6,6 +6,13 @@
     srcs = [
         "mirror_lib.py",
     ],
+    data = [
+        "@com_github_bazelbuild_buildtools//buildifier",
+    ],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
+    deps = [
+        "@bazel_tools//tools/python/runfiles",
+    ],
 )
 
 py_binary(
@@ -25,13 +32,12 @@
         "mirror_go_repos.py",
     ],
     data = [
-        "@com_github_bazelbuild_buildtools//buildifier",
         "@go_sdk//:bin/go",
     ],
     target_compatible_with = ["@platforms//cpu:x86_64"],
+    visibility = ["//visibility:public"],
     deps = [
         ":mirror_lib",
-        "@bazel_tools//tools/python/runfiles",
     ],
 )
 
diff --git a/tools/go/go_mirrors.bzl b/tools/go/go_mirrors.bzl
index 8865d69..bfee0a9 100644
--- a/tools/go/go_mirrors.bzl
+++ b/tools/go/go_mirrors.bzl
@@ -147,13 +147,6 @@
         "strip_prefix": "github.com/grpc-ecosystem/grpc-gateway@v1.16.0",
         "version": "v1.16.0",
     },
-    "com_github_joho_godotenv": {
-        "filename": "com_github_joho_godotenv__v1.4.0.zip",
-        "importpath": "github.com/joho/godotenv",
-        "sha256": "6c6d2f6c2a9d2ee8608e4acd7ba7035d31b1f0da3c7d9537a32928b8eed4e3cd",
-        "strip_prefix": "github.com/joho/godotenv@v1.4.0",
-        "version": "v1.4.0",
-    },
     "com_github_mattn_go_sqlite3": {
         "filename": "com_github_mattn_go_sqlite3__v1.14.10.zip",
         "importpath": "github.com/mattn/go-sqlite3",
diff --git a/tools/go/mirror_go_repos.py b/tools/go/mirror_go_repos.py
index 52e9e26..ae8f722 100644
--- a/tools/go/mirror_go_repos.py
+++ b/tools/go/mirror_go_repos.py
@@ -14,9 +14,6 @@
 import sys
 import tarfile
 from typing import List, Dict
-import urllib.request
-
-from bazel_tools.tools.python.runfiles import runfiles
 
 # Need a fully qualified import here because @bazel_tools interferes.
 import org_frc971.tools.go.mirror_lib
@@ -101,7 +98,14 @@
 
 def main(argv):
     parser = argparse.ArgumentParser()
-    parser.add_argument(
+    group = parser.add_mutually_exclusive_group()
+    group.add_argument(
+        "--prune",
+        action="store_true",
+        help=("When set, makes the tool prune go_mirrors_bzl to match the "
+              "repositories specified in go_deps_bzl. Incompatible with "
+              "--ssh_host."))
+    group.add_argument(
         "--ssh_host",
         type=str,
         help=("The SSH host to copy the downloaded Go repositories to. This "
@@ -121,37 +125,38 @@
     else:
         existing_mirrored_repos = {}
 
-    with tarfile.open("go_deps.tar", "w") as tar:
-        cached_info = download_repos(repos, existing_mirrored_repos, tar)
-        num_not_already_mirrored = len(tar.getnames())
+    exit_code = 0
 
-    print(f"Found {num_not_already_mirrored}/{len(cached_info)} libraries "
-          "that need to be mirrored.")
-
-    # Only mirror the deps if we've specified an SSH host and we actually have
-    # something to mirror.
-    if args.ssh_host and num_not_already_mirrored:
-        copy_to_host_and_unpack("go_deps.tar", args.ssh_host)
+    if args.prune:
+        # Delete all mirror info that is not needed anymore.
+        existing_cache_info = org_frc971.tools.go.mirror_lib.parse_go_mirror_info(args.go_mirrors_bzl)
+        cached_info = {}
+        for repo in repos:
+            try:
+                cached_info[repo["name"]] = existing_cache_info[repo["name"]]
+            except KeyError:
+                print(f"{repo['name']} needs to be mirrored still.")
+                exit_code = 1
     else:
-        print("Skipping mirroring because of lack of --ssh_host or there's "
-              "nothing to actually mirror.")
+        # Download all the repositories that need to be mirrored.
+        with tarfile.open("go_deps.tar", "w") as tar:
+            cached_info = download_repos(repos, existing_mirrored_repos, tar)
+            num_not_already_mirrored = len(tar.getnames())
 
-    with open(args.go_mirrors_bzl, "w") as file:
-        file.write("# This file is auto-generated. Do not edit.\n")
-        file.write("GO_MIRROR_INFO = ")
-        # Format as JSON first. It's parsable as Starlark.
-        json.dump(cached_info, file, indent=4, sort_keys=True)
-        file.write("\n")
+        print(f"Found {num_not_already_mirrored}/{len(cached_info)} libraries "
+              "that need to be mirrored.")
 
+        # Only mirror the deps if we've specified an SSH host and we actually have
+        # something to mirror.
+        if args.ssh_host and num_not_already_mirrored:
+            copy_to_host_and_unpack("go_deps.tar", args.ssh_host)
+        else:
+            print("Skipping mirroring because of lack of --ssh_host or there's "
+                  "nothing to actually mirror.")
 
-    # Properly format the file now so that the linter doesn't complain.
-    r = runfiles.Create()
-    subprocess.run(
-        [
-            r.Rlocation("com_github_bazelbuild_buildtools/buildifier/buildifier_/buildifier"),
-            args.go_mirrors_bzl,
-        ],
-        check=True)
+    org_frc971.tools.go.mirror_lib.write_go_mirror_info(args.go_mirrors_bzl, cached_info)
+
+    return exit_code
 
 
 if __name__ == "__main__":
diff --git a/tools/go/mirror_lib.py b/tools/go/mirror_lib.py
index faad896..ea23abc 100644
--- a/tools/go/mirror_lib.py
+++ b/tools/go/mirror_lib.py
@@ -1,7 +1,11 @@
 """Provides helper functions for mirroring Go repositories."""
 
-import unittest.mock
+import json
+import subprocess
 from typing import List, Dict
+import unittest.mock
+
+from bazel_tools.tools.python.runfiles import runfiles
 
 
 def read_file(filepath: str) -> str:
@@ -39,3 +43,30 @@
 
     return repositories
 
+
+def parse_go_mirror_info(filepath: str) -> Dict[str, Dict[str, str]]:
+    """Parses the tools/go/go_mirrors.bzl file and returns the GO_MIRROR_INFO dictionary."""
+    global_data = {}
+    compiled_code = compile(read_file(filepath), filepath, "exec")
+    eval(compiled_code, global_data)
+
+    return global_data["GO_MIRROR_INFO"]
+
+
+def write_go_mirror_info(filepath: str, mirror_info: Dict[str, Dict[str, str]]):
+    """Saves the specified mirror_info as GO_MIRROR_INFO into tools/go/go_mirrors.bzl."""
+    with open(filepath, "w") as file:
+        file.write("# This file is auto-generated. Do not edit.\n")
+        file.write("GO_MIRROR_INFO = ")
+        # Format as JSON first. It's parsable as Starlark.
+        json.dump(mirror_info, file, indent=4, sort_keys=True)
+        file.write("\n")
+
+    # Properly format the file now so that the linter doesn't complain.
+    r = runfiles.Create()
+    subprocess.run(
+        [
+            r.Rlocation("com_github_bazelbuild_buildtools/buildifier/buildifier_/buildifier"),
+            filepath,
+        ],
+        check=True)
diff --git a/tools/go/tweak_gazelle_go_deps.py b/tools/go/tweak_gazelle_go_deps.py
index 7189d43..d9d7901 100644
--- a/tools/go/tweak_gazelle_go_deps.py
+++ b/tools/go/tweak_gazelle_go_deps.py
@@ -12,14 +12,14 @@
 import sys
 import textwrap
 
-import tools.go.mirror_lib
+import org_frc971.tools.go.mirror_lib
 
 def main(argv):
     parser = argparse.ArgumentParser()
     parser.add_argument("go_deps_bzl", type=str)
     args = parser.parse_args(argv[1:])
 
-    repos = tools.go.mirror_lib.parse_go_repositories(args.go_deps_bzl)
+    repos = org_frc971.tools.go.mirror_lib.parse_go_repositories(args.go_deps_bzl)
 
     with open(args.go_deps_bzl, "w") as file:
         file.write(textwrap.dedent("""\