Update how we determine flutter candidate version (#7989)

.github/workflows/flutter-prep.yaml

diff --git a/.github/workflows/flutter-prep.yaml b/.github/workflows/flutter-prep.yaml
index ab3e928..6e7bcc3 100644
--- a/.github/workflows/flutter-prep.yaml
+++ b/.github/workflows/flutter-prep.yaml
@@ -33,11 +33,8 @@
 
       - name: Get Latest Flutter Candidate
         id: flutter-candidate
-        # TODO(https://github.com/flutter/devtools/issues/7939): Switch back to using
-        # LATEST_FLUTTER_CANDIDATE=$(./tool/latest_flutter_candidate.sh)
-        # once Flutter rolls are tagged again:
         run: |
-          LATEST_FLUTTER_CANDIDATE=1c77696615558bf8f9fa7a6e2a473f438f1c03ca
+          LATEST_FLUTTER_CANDIDATE=$(./tool/latest_flutter_candidate.sh)
           echo "FLUTTER_CANDIDATE=$LATEST_FLUTTER_CANDIDATE" >> $GITHUB_OUTPUT
 
       - name: Load Cached Flutter SDK

CONTRIBUTING.md

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 9a40bba..5dff668 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -89,6 +89,10 @@
 ### Workflow for making changes
 
 1. Change your local Flutter SDK to the latest flutter candidate branch: `devtools_tool update-flutter-sdk --from-path`
+
+> Note: Until  https://github.com/flutter/devtools/issues/7939 is fixed, run
+`devtools_tool update-flutter-sdk --use-cache` instead.
+
 2. Create a branch from your cloned DevTools repo: `git checkout -b myBranch`
 3. Ensure your branch, dependencies, and generated code are up-to-date: `devtools_tool sync`
 4. Implement your changes, and commit to your branch: `git commit -m “description”`

flutter-candidate.txt

diff --git a/flutter-candidate.txt b/flutter-candidate.txt
index 8d84894..d97ed57 100644
--- a/flutter-candidate.txt
+++ b/flutter-candidate.txt
@@ -1 +1 @@
-3.23.0-12.0.pre
+1c77696615558bf8f9fa7a6e2a473f438f1c03ca

tool/RELEASE_INSTRUCTIONS.md

diff --git a/tool/RELEASE_INSTRUCTIONS.md b/tool/RELEASE_INSTRUCTIONS.md
index 8f139d3..6a5117b 100644
--- a/tool/RELEASE_INSTRUCTIONS.md
+++ b/tool/RELEASE_INSTRUCTIONS.md
@@ -1,4 +1,4 @@
-> [!NOTE] 
+> [!NOTE]
 > There are parts of this release process that can only be completed by Googlers
 on the Dash team. If you are not a Googler on the Dash team, please reach out on the
 [#hackers-devtools](https://discord.com/channels/608014603317936148/1106667330093723668)
@@ -69,6 +69,8 @@
    git checkout main; git rebase-update
    ```
 
+> Note: Until https://github.com/flutter/devtools/issues/7939, skip this step.
+
 2. Your Flutter SDK in `devtools/tool/flutter-sdk` and the one on PATH are updated to the latest candidate release branch:
    ```shell
    devtools_tool update-flutter-sdk --update-on-path
@@ -91,6 +93,15 @@
    - create a PR for release changes
    - update your local version of flutter to the latest flutter candidate
 
+**The following is required until https://github.com/flutter/devtools/issues/7939 is fixed:**
+
+1. Update the `flutter-candidate.txt` to the latest Flutter candidate in g3 (see instructions in DevTools Release Rotation email). This change should get committed with the DevTools release PR so that we know which version it was released with.
+
+2. Update your Flutter SDK in `devtools/tool/flutter-sdk` and the one on PATH to the latest Flutter candidate:
+   ```shell
+   devtools_tool update-flutter-sdk --update-on-path --use-cache
+   ```
+
 #### Verify the version changes for the Release PR
 
 Verify the changes in the release PR contain:

tool/latest_flutter_candidate.sh

diff --git a/tool/latest_flutter_candidate.sh b/tool/latest_flutter_candidate.sh
index f709d24..b90012e 100755
--- a/tool/latest_flutter_candidate.sh
+++ b/tool/latest_flutter_candidate.sh
@@ -9,12 +9,17 @@
 
 # To determine the most recent candidate available on g3 find the largest
 # tag that matches the version X.Y.Z-M.N.pre, where Z=0 and N=0.(i.e. X.Y.0-M.0.pre)
-LATEST_FLUTTER_CANDIDATE=$(git ls-remote --tags --sort='-v:refname' https://flutter.googlesource.com/mirrors/flutter/ \
-  | grep -E "refs/tags/[0-9]+.[0-9]+.0-[0-9]+.0.pre" \
-  | cut -f2 \
-  | sort --version-sort \
-  | tail -n1 \
-  | sed 's/^.*\(flutter.*\)$/\1/'\
-  )
+
+# TODO(https://github.com/flutter/devtools/issues/7939): Switch back to using the
+# commented out git command below once Flutter rolls are tagged again:
+LATEST_FLUTTER_CANDIDATE=`cat ./flutter-candidate.txt`
+
+# LATEST_FLUTTER_CANDIDATE=$(git ls-remote --tags --sort='-v:refname' https://flutter.googlesource.com/mirrors/flutter/ \
+#   | grep -E "refs/tags/[0-9]+.[0-9]+.0-[0-9]+.0.pre" \
+#   | cut -f2 \
+#   | sort --version-sort \
+#   | tail -n1 \
+#   | sed 's/^.*\(flutter.*\)$/\1/'\
+#   )
 
 echo $LATEST_FLUTTER_CANDIDATE