From 1d43a6b105829920efeb6d98fe2f2929f16e48c2 Mon Sep 17 00:00:00 2001
From: Adam Dinwoodie <adam@dinwoodie.org>
Date: Mon, 9 Jan 2023 23:20:00 +0000
Subject: [PATCH 1/4] Add package caching

To speed up Cygwin installations, allow users to store the downloaded
packages using GitHub's caching, rather than needing the packages to be
downloaded from the Cygwin mirrors on every run.

This speeds up the installation when there's a good cache hit, at the
expense of adding some additional complexity, and using the limited
cache space (although with 10GB assigned to every repository on GitHub,
I can't imagine most folk are getting close to the limit!).

To avoid unnecessary cache churn, the new steps check if the cache has
actually meaningfully changed before storing a new cache.  This uses
b2sum for speed, since we're just checking for unexpected changes in the
cache, and we don't need cryptographic security.
---
 .github/workflows/test.yml | 31 +++++++++++++++++++++++++++
 README.md                  | 17 +++++++++++++++
 action.yml                 | 43 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 429026c..e3f53f6 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -228,3 +228,34 @@ jobs:
       shell: bash
       env:
         SHELLOPTS: igncr
+
+  caching:
+    runs-on: windows-latest
+
+    name: 'Test use of the cache'
+
+    steps:
+      - run: git config --global core.autocrlf input
+      - uses: actions/checkout@v2
+      - name: Install Cygwin and bash-completion
+        uses: ./
+        with:
+          packages: bash-completion
+          package-cache-key: testing-cache
+          add-to-path: false
+      - name: Delete Cygwin installation and cache
+        run: |
+          Remove-Item -Force -Recurse C:\cygwin
+          Remove-Item -Force -Recurse C:\cygwin-packages
+      - name: Reinstall Cygwin only
+        uses: ./
+        with:
+          package-cache-key: testing-cache
+          add-to-path: false
+      - name: Find bash-completion in the package cache
+        shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
+        run: |
+          for file in /cygdrive/c/cygwin-packages/*/*/*/bash-completion/bash-completion-*.tar.*; do
+            [[ -f "$file" ]] && exit 0  # File actually exists
+          done
+          exit 1  # No such downloaded file
diff --git a/README.md b/README.md
index 54b1b66..2df1308 100644
--- a/README.md
+++ b/README.md
@@ -26,6 +26,7 @@ Parameters
 | site        | http://mirrors.kernel.org/sourceware/cygwin/ | Mirror site to install from
 | check-sig   | true                                         | Whether to check the setup.ini signature
 | add-to-path | true                                         | Whether to add Cygwin's `/bin` directory to the system `PATH`
+| package-cache-key | ''                                     | The key to use for caching downloaded packages.
 
 Line endings
 ------------
@@ -85,6 +86,22 @@ those executables directly in a `run:` in your workflow. Execute them via
 Alternatively, putting e.g. `CYGWIN=winsymlinks:native` into the workflow's
 environment works, since setup now honours that.
 
+Caching
+-------
+
+If you're likely to do regular builds, you might want to store the packages
+locally rather than needing to download them from the Cygwin mirrors on every
+build.  Set `package-cache-key` to some string (e.g. `cygwin-package-cache`),
+and the action will use [GitHub's dependency caching][0] to store downloaded
+package files between runs.
+
+[0]: https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows
+
+This has the effect of speeding up the run of the installation itself, at the
+expense of taking slightly longer before and after the installation to check
+and potentially update the cache.  The installer will still check for updated
+packages, and will download new packages if the cached ones are out of date
+
 Mirrors and signatures
 ----------------------
 
diff --git a/action.yml b/action.yml
index a6b6b95..8cef84c 100644
--- a/action.yml
+++ b/action.yml
@@ -26,10 +26,33 @@ inputs:
     description: Should Cygwin's bin directory be added to the system PATH?
     required: false
     default: true
+  package-cache-key:
+    description: Key prefix to use for package caches
+    required: false
+    default: ''
 
 runs:
   using: "composite"
   steps:
+    - uses: actions/cache/restore@v3
+      if: inputs.package-cache-key != ''
+      with:
+        key: ${{ inputs.package-cache-key }}-${{ github.run_id }}-${{ github.run_attempt }}
+        path: C:\cygwin-packages
+        restore-keys:
+          ${{ inputs.package-cache-key }}-${{ github.run_id }}-
+          ${{ inputs.package-cache-key }}-
+
+    - if: inputs.package-cache-key != ''
+      working-directory: C:\
+      shell: bash
+      run: |
+        if [[ -d cygwin-packages ]]; then
+          find cygwin-packages -type f ! -name setup.ini -print0 |
+            sort -z |
+            xargs -0 b2sum >cygwin-packages-checksum.old
+        fi
+
     - run: |
         $platform = '${{ inputs.platform }}'
         $platform = $platform -replace '^(x64|amd64)$', 'x86_64'
@@ -82,6 +105,26 @@ runs:
         & C:\setup.exe $args | Out-Default
       shell: powershell
 
+    - if: inputs.package-cache-key != ''
+      id: refresh-cache
+      working-directory: C:\
+      shell: bash
+      run: |
+        if [[ -d cygwin-packages ]]; then
+          find cygwin-packages -type f ! -name setup.ini -print0 |
+            sort -z |
+            xargs -0 b2sum >cygwin-packages-checksum.new
+          if ! diff cygwin-packages-checksum.old cygwin-packages-checksum.new; then
+            printf 'update_package_cache=YesPlease\n' >>"$GITHUB_OUTPUT"
+          fi
+        fi
+
+    - if: steps.refresh-cache.outputs.update_package_cache != ''
+      uses: actions/cache/save@v3
+      with:
+        key: ${{ inputs.package-cache-key }}-${{ github.run_id }}-${{ github.run_attempt }}
+        path: C:\cygwin-packages
+
     - if: ${{ inputs.add-to-path  == 'true' }}
       run: echo "${{ inputs.install-dir }}\bin" >> $env:GITHUB_PATH
       shell: powershell

From 8ad2694ccd6d4138995bfc452e7e0f84164f32ce Mon Sep 17 00:00:00 2001
From: Adam Dinwoodie <adam@dinwoodie.org>
Date: Tue, 10 Jan 2023 21:31:53 +0000
Subject: [PATCH 2/4] Allow save-only/restore-only cache runs

Add an option to restore a cache without creating a new one, or to
create a cache without restoring an old one.  This is useful in the
scenario where the action is called multiple times in a run, as it
allows the cache to only be restored on the first call, and for a new
cache to only be written on the last call.

This option replaces the `package-cache-key` option; as discussed in #6
that option isn't very useful.

Additionally, add some more scopes to the cache name.  Without this
change, a second attempt to create a cache in the same action run (e.g.
because one step installs some packages, then another step installs some
more) will fail because of the cache name collision.

Also update the README and tests, although the tests are only getting a
very quick update for this function, as I'm going to do a much more
comprehensive test update separately.
---
 .github/workflows/test.yml |  4 ++--
 README.md                  | 42 +++++++++++++++++++++++++++-----------
 action.yml                 | 22 +++++++++++---------
 3 files changed, 44 insertions(+), 24 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index e3f53f6..4e10473 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -241,7 +241,7 @@ jobs:
         uses: ./
         with:
           packages: bash-completion
-          package-cache-key: testing-cache
+          package-cache: enabled
           add-to-path: false
       - name: Delete Cygwin installation and cache
         run: |
@@ -250,7 +250,7 @@ jobs:
       - name: Reinstall Cygwin only
         uses: ./
         with:
-          package-cache-key: testing-cache
+          package-cache-key: enabled
           add-to-path: false
       - name: Find bash-completion in the package cache
         shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
diff --git a/README.md b/README.md
index 2df1308..138623c 100644
--- a/README.md
+++ b/README.md
@@ -18,15 +18,15 @@ Please fix my terrible cargo-cult PowerShell.
 Parameters
 ----------
 
-| Input       | Default                                      | Description
-| ----------- | -------------------------------------------- | -----------
-| platform    | x86_64                                       | Install the x86 or x86\_64 version of Cygwin.
-| packages    | *none*                                       | List of additional packages to install.
-| install-dir | C:\cygwin                                    | Installation directory
-| site        | http://mirrors.kernel.org/sourceware/cygwin/ | Mirror site to install from
-| check-sig   | true                                         | Whether to check the setup.ini signature
-| add-to-path | true                                         | Whether to add Cygwin's `/bin` directory to the system `PATH`
-| package-cache-key | ''                                     | The key to use for caching downloaded packages.
+| Input         | Default                                      | Description
+| ------------- | -------------------------------------------- | -----------
+| platform      | x86_64                                       | Install the x86 or x86\_64 version of Cygwin.
+| packages      | *none*                                       | List of additional packages to install.
+| install-dir   | C:\cygwin                                    | Installation directory
+| site          | http://mirrors.kernel.org/sourceware/cygwin/ | Mirror site to install from
+| check-sig     | true                                         | Whether to check the setup.ini signature
+| add-to-path   | true                                         | Whether to add Cygwin's `/bin` directory to the system `PATH`
+| package-cache | disabled                                     | Whether to cache the package downloads
 
 Line endings
 ------------
@@ -91,9 +91,8 @@ Caching
 
 If you're likely to do regular builds, you might want to store the packages
 locally rather than needing to download them from the Cygwin mirrors on every
-build.  Set `package-cache-key` to some string (e.g. `cygwin-package-cache`),
-and the action will use [GitHub's dependency caching][0] to store downloaded
-package files between runs.
+build.  Set `package-cache` to `enabled` and the action will use [GitHub's
+dependency caching][0] to store downloaded package files between runs.
 
 [0]: https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows
 
@@ -102,6 +101,25 @@ expense of taking slightly longer before and after the installation to check
 and potentially update the cache.  The installer will still check for updated
 packages, and will download new packages if the cached ones are out of date
 
+In certain circumstances you might want to ignore any existing caches but still
+store a new one, or restore a cache but not write one.  Do this by setting
+`package-cache` to `saveonly` or `restoreonly` as appropriate.  This is
+particularly useful when calling the action multiple times in the same run,
+where you probably want to restore the cache the first time the action is
+called, then save it the last time it is called.
+
+You should make sure to clear these caches every so often.  This action, like
+the underlying Cygwin installer, doesn't remove old package files from its
+download directory, so if you don't clear the caches occasionally (and you run
+builds often enough that GitHub doesn't do it for you automatically) you'll
+find the caches keep getting larger as they gain more and more outdated and
+unused packages.  Either [delete them manually][1], [use a separate action or
+API call][2], or do occasional runs with `saveonly` to create a fresher small
+cache.
+
+[1]: https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#deleting-cache-entries
+[2]: https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#deleting-cache-entries
+
 Mirrors and signatures
 ----------------------
 
diff --git a/action.yml b/action.yml
index 8cef84c..31bab52 100644
--- a/action.yml
+++ b/action.yml
@@ -26,24 +26,26 @@ inputs:
     description: Should Cygwin's bin directory be added to the system PATH?
     required: false
     default: true
-  package-cache-key:
-    description: Key prefix to use for package caches
+  package-cache:
+    description: Cache package downloads for speed
     required: false
-    default: ''
+    default: disabled
 
 runs:
   using: "composite"
   steps:
     - uses: actions/cache/restore@v3
-      if: inputs.package-cache-key != ''
+      if: inputs.package-cache-behaviour == 'enabled' || inputs.package-cache-behaviour == 'restoreonly'
       with:
-        key: ${{ inputs.package-cache-key }}-${{ github.run_id }}-${{ github.run_attempt }}
+        key: cygwin-install-action-packages-${{ github.run_id }}-${{ github.run_attempt }}-${{ github.job }}-${{ github.action }}
         path: C:\cygwin-packages
         restore-keys:
-          ${{ inputs.package-cache-key }}-${{ github.run_id }}-
-          ${{ inputs.package-cache-key }}-
+          cygwin-install-action-packages-${{ github.run_id }}-${{ github.job }}-${{ github.run_attempt }}-
+          cygwin-install-action-packages-${{ github.run_id }}-${{ github.job }}-
+          cygwin-install-action-packages-${{ github.run_id }}-
+          cygwin-install-action-packages-
 
-    - if: inputs.package-cache-key != ''
+    - if: inputs.package-cache-behaviour == 'enabled' || inputs.package-cache-behaviour == 'restoreonly'
       working-directory: C:\
       shell: bash
       run: |
@@ -105,7 +107,7 @@ runs:
         & C:\setup.exe $args | Out-Default
       shell: powershell
 
-    - if: inputs.package-cache-key != ''
+    - if: inputs.package-cache-behaviour == 'enabled' || inputs.package-cache-behaviour == 'saveonly'
       id: refresh-cache
       working-directory: C:\
       shell: bash
@@ -122,7 +124,7 @@ runs:
     - if: steps.refresh-cache.outputs.update_package_cache != ''
       uses: actions/cache/save@v3
       with:
-        key: ${{ inputs.package-cache-key }}-${{ github.run_id }}-${{ github.run_attempt }}
+        key: cygwin-install-action-packages-${{ github.run_id }}-${{ github.run_attempt }}-${{ github.job }}-${{ github.action }}
         path: C:\cygwin-packages
 
     - if: ${{ inputs.add-to-path  == 'true' }}

From 0066f6723e597c81b4dc4b0bf9d5cb57870c69ac Mon Sep 17 00:00:00 2001
From: Adam Dinwoodie <adam@dinwoodie.org>
Date: Tue, 10 Jan 2023 22:15:53 +0000
Subject: [PATCH 3/4] Add much more comprehensive cache testing

---
 .github/workflows/cache-test.yml | 193 +++++++++++++++++++++++++++++++
 .github/workflows/test.yml       |  31 -----
 2 files changed, 193 insertions(+), 31 deletions(-)
 create mode 100644 .github/workflows/cache-test.yml

diff --git a/.github/workflows/cache-test.yml b/.github/workflows/cache-test.yml
new file mode 100644
index 0000000..7befc8c
--- /dev/null
+++ b/.github/workflows/cache-test.yml
@@ -0,0 +1,193 @@
+name: Caching tests
+
+on: [push, pull_request]
+
+# Ensure there's only a single version of this running in any repo, so one set
+# of tests won't create or destroy caches that interfere with another run.
+concurrency: caches
+
+jobs:
+  clear-caches:
+    runs-on: ubuntu-latest
+    permissions:
+      actions: write
+    steps:
+      # This will only delete up to 100 caches.  That should be far more than
+      # is ever needed.
+      - name: Delete cache entries
+        uses: actions/github-script@v6
+        with:
+          script: |
+            const response = await github.rest.actions.getActionsCacheList({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              per_page: 100,
+              key: 'cygwin-install-action-packages-'
+            });
+            for (const cache of response.data.actions_caches) {
+              await github.rest.actions.deleteActionsCacheById({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                cache_id: cache.id
+              });
+            }
+
+  test-caching:
+    runs-on: windows-latest
+
+    needs: clear-caches
+
+    # Ordering is important here to ensure the correct things are in the
+    # correct caches at the correct times.
+    #
+    # This also relies on having six Cygwin packages that don't have any
+    # cross-dependencies (and ideally are small and have few dependencies of
+    # their own), so we can distinguish what's cached at what step.
+    #
+    # We test for the correct behaviour in the following circumstances:
+    #
+    # option      | saves   | restores
+    # ------------+---------+----------
+    # disabled    | no (1)  | no (5)
+    # enabled     | yes (2) | yes (6)
+    # saveonly    | yes (3) | no (7)
+    # restoreonly | no (4)  | yes (8)
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Install Cygwin + bash_completion, no caching
+        uses: ./
+        with:
+          packages: bash-completion
+          package-cache: disabled
+
+      - name: Delete the Cygwin installation and downloaded packages
+        run: |
+          Remove-Item -Force -Recurse C:\cygwin
+          Remove-Item -Force -Recurse C:\cygwin-packages
+          Remove-Item -Force -Recurse C:\cygwin-packages-checksum.*
+
+      - name: Install Cygwin + brotli, with caching
+        uses: ./
+        with:
+          packages: brotli
+          package-cache: enabled
+
+      # This assumes 6 and tests 1
+      - name: Ensure bash-completion not downloaded
+        shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
+        run: |
+          for file in /cygdrive/c/cygwin-packages/*/*/*/*/bash-completion-*.tar.*; do
+            [[ -f "$file" ]] && exit 1
+          done
+          exit 0
+
+      - name: Delete the Cygwin installation and downloaded packages
+        run: |
+          Remove-Item -Force -Recurse C:\cygwin
+          Remove-Item -Force -Recurse C:\cygwin-packages
+          Remove-Item -Force -Recurse C:\cygwin-packages-checksum.*
+
+      - name: Install Cygwin + libyajl2, with caching
+        uses: ./
+        with:
+          packages: libyajl2
+          package-cache: enabled
+
+      # This tests 2 and 6
+      - name: Ensure brotli downloaded
+        shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
+        run: |
+          for file in /cygdrive/c/cygwin-packages/*/*/*/*/brotli-*.tar.*; do
+            [[ -f "$file" ]] && exit 0
+          done
+          exit 1
+
+      - name: Delete the Cygwin installation and downloaded packages
+        run: |
+          Remove-Item -Force -Recurse C:\cygwin
+          Remove-Item -Force -Recurse C:\cygwin-packages
+          Remove-Item -Force -Recurse C:\cygwin-packages-checksum.*
+
+      - name: Install Cygwin + mksh, saveonly
+        uses: ./
+        with:
+          packages: mksh
+          package-cache: saveonly
+
+      # This assumes 2 and tests 7
+      - name: Ensure libyajl2 not downloaded
+        shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
+        run: |
+          for file in /cygdrive/c/cygwin-packages/*/*/*/*/libyajl2-*.tar.*; do
+            [[ -f "$file" ]] && exit 1
+          done
+          exit 0
+
+      - name: Delete the Cygwin installation and downloaded packages
+        run: |
+          Remove-Item -Force -Recurse C:\cygwin
+          Remove-Item -Force -Recurse C:\cygwin-packages
+          Remove-Item -Force -Recurse C:\cygwin-packages-checksum.*
+
+      - name: Install Cygwin + libgif7, restoreonly
+        uses: ./
+        with:
+          packages: libgif7
+          package-cache: restoreonly
+
+      # This tests 3 and 8
+      - name: Ensure mksh downloaded
+        shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
+        run: |
+          for file in /cygdrive/c/cygwin-packages/*/*/*/*/mksh-*.tar.*; do
+            [[ -f "$file" ]] && exit 1
+          done
+          exit 0
+
+      - name: Delete the Cygwin installation and downloaded packages
+        run: |
+          Remove-Item -Force -Recurse C:\cygwin
+          Remove-Item -Force -Recurse C:\cygwin-packages
+          Remove-Item -Force -Recurse C:\cygwin-packages-checksum.*
+
+      - name: Install Cygwin, restoreonly
+        uses: ./
+        with:
+          package-cache: restoreonly
+
+      # This assumes 8 and tests 4
+      - name: Ensure libgif7 not downloaded
+        shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
+        run: |
+          for file in /cygdrive/c/cygwin-packages/*/*/*/*/libgif7-*.tar.*; do
+            [[ -f "$file" ]] && exit 1
+          done
+          exit 0
+
+      - name: Delete the Cygwin installation and downloaded packages
+        run: |
+          Remove-Item -Force -Recurse C:\cygwin
+          Remove-Item -Force -Recurse C:\cygwin-packages
+          Remove-Item -Force -Recurse C:\cygwin-packages-checksum.*
+
+      - name: Install Cygwin, caching disabled
+        uses: ./
+        with:
+          package-cache: disabled
+
+      # This assumes 3 and tests 5
+      - name: Ensure mksh not downloaded
+        shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
+        run: |
+          for file in /cygdrive/c/cygwin-packages/*/*/*/*/mksh-*.tar.*; do
+            [[ -f "$file" ]] && exit 1
+          done
+          exit 0
+
+      - name: Delete the Cygwin installation and downloaded packages
+        run: |
+          Remove-Item -Force -Recurse C:\cygwin
+          Remove-Item -Force -Recurse C:\cygwin-packages
+          Remove-Item -Force -Recurse C:\cygwin-packages-checksum.*
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 4e10473..429026c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -228,34 +228,3 @@ jobs:
       shell: bash
       env:
         SHELLOPTS: igncr
-
-  caching:
-    runs-on: windows-latest
-
-    name: 'Test use of the cache'
-
-    steps:
-      - run: git config --global core.autocrlf input
-      - uses: actions/checkout@v2
-      - name: Install Cygwin and bash-completion
-        uses: ./
-        with:
-          packages: bash-completion
-          package-cache: enabled
-          add-to-path: false
-      - name: Delete Cygwin installation and cache
-        run: |
-          Remove-Item -Force -Recurse C:\cygwin
-          Remove-Item -Force -Recurse C:\cygwin-packages
-      - name: Reinstall Cygwin only
-        uses: ./
-        with:
-          package-cache-key: enabled
-          add-to-path: false
-      - name: Find bash-completion in the package cache
-        shell: C:\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -o igncr {0}
-        run: |
-          for file in /cygdrive/c/cygwin-packages/*/*/*/bash-completion/bash-completion-*.tar.*; do
-            [[ -f "$file" ]] && exit 0  # File actually exists
-          done
-          exit 1  # No such downloaded file

From 76f43bad2ff65199071a673131a589494717b089 Mon Sep 17 00:00:00 2001
From: Adam Dinwoodie <adam@dinwoodie.org>
Date: Tue, 10 Jan 2023 22:42:36 +0000
Subject: [PATCH 4/4] Add cache performance testing

This should hopefully show how much of a difference, if any, caching
packages makes.  There's no automated comparison here, the test just
runs one install without a cache, then a second install with a cache,
then a human needs to look at what difference it makes.
---
 .github/workflows/cache-perf.yml   | 48 ++++++++++++++++++++++++++++++
 .github/workflows/cache-test.yml   | 22 +-------------
 .github/workflows/clear-caches.yml | 29 ++++++++++++++++++
 3 files changed, 78 insertions(+), 21 deletions(-)
 create mode 100644 .github/workflows/cache-perf.yml
 create mode 100644 .github/workflows/clear-caches.yml

diff --git a/.github/workflows/cache-perf.yml b/.github/workflows/cache-perf.yml
new file mode 100644
index 0000000..2a1d78a
--- /dev/null
+++ b/.github/workflows/cache-perf.yml
@@ -0,0 +1,48 @@
+name: Cache performance testing
+
+# Only run manually: the purpose of this test is to check how much (if at all)
+# using the caches helps, and that's not something that needs doing often, and
+# it is something that's time consuming.
+on: workflow_dispatch
+
+# Avoid running at the same time as other actions that interfere with caches,
+# to avoid pollution.
+concurrency: caches
+
+jobs:
+  clear-caches:
+    uses: ./.github/workflows/clear-caches.yml
+    permissions:
+      actions: write
+
+  # There should now be no cache, so we can test how long it takes to do an
+  # install without a cache while building the cache for the later action.
+  install-without-cache:
+    runs-on: windows-latest
+    needs: clear-caches
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Install a large set of Cygwin packages
+        uses: ./
+        with:
+          packages: >
+            biber doxygen evolution kde-dev-utils
+            mkvtoolnix-debuginfo nghttp x11vnc
+          package-cache: saveonly
+
+  install-with-cache:
+    runs-on: windows-latest
+    needs: install-without-cache
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Install a large set of Cygwin packages
+        uses: ./
+        with:
+          packages: >
+            biber doxygen evolution kde-dev-utils
+            mkvtoolnix-debuginfo nghttp x11vnc
+          package-cache: enabled
diff --git a/.github/workflows/cache-test.yml b/.github/workflows/cache-test.yml
index 7befc8c..212d046 100644
--- a/.github/workflows/cache-test.yml
+++ b/.github/workflows/cache-test.yml
@@ -8,29 +8,9 @@ concurrency: caches
 
 jobs:
   clear-caches:
-    runs-on: ubuntu-latest
+    uses: ./.github/workflows/clear-caches.yml
     permissions:
       actions: write
-    steps:
-      # This will only delete up to 100 caches.  That should be far more than
-      # is ever needed.
-      - name: Delete cache entries
-        uses: actions/github-script@v6
-        with:
-          script: |
-            const response = await github.rest.actions.getActionsCacheList({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              per_page: 100,
-              key: 'cygwin-install-action-packages-'
-            });
-            for (const cache of response.data.actions_caches) {
-              await github.rest.actions.deleteActionsCacheById({
-                owner: context.repo.owner,
-                repo: context.repo.repo,
-                cache_id: cache.id
-              });
-            }
 
   test-caching:
     runs-on: windows-latest
diff --git a/.github/workflows/clear-caches.yml b/.github/workflows/clear-caches.yml
new file mode 100644
index 0000000..12c2d24
--- /dev/null
+++ b/.github/workflows/clear-caches.yml
@@ -0,0 +1,29 @@
+name: Clear Cygwin package caches
+
+on: workflow_call
+
+jobs:
+  clear-caches:
+    runs-on: ubuntu-latest
+    permissions:
+      actions: write
+    steps:
+      # This will only delete up to 100 caches.  That should be far more than
+      # is ever needed.
+      - name: Delete cache entries
+        uses: actions/github-script@v6
+        with:
+          script: |
+            const response = await github.rest.actions.getActionsCacheList({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              per_page: 100,
+              key: 'cygwin-install-action-packages-'
+            });
+            for (const cache of response.data.actions_caches) {
+              await github.rest.actions.deleteActionsCacheById({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                cache_id: cache.id
+              });
+            }