CDT has been reformatted!

Eclipse CDT has just had all its source code reformatted. That means I just pushed a massive set of commits with a huge git shortstat:

$ git diff --shortstat  3cf0297769..HEAD
 10806 files changed, 697885 insertions(+), 593225 deletions(-)

That also means that any commit/patch you have on CDT before the reformat will almost certainly not apply cleanly.

Therefore I have created this guide for you to reformat your commit and make it easier for you to submit your updated patch to gerrit.

To be able to rebase your commit onto the current master you need to create a version of it with the new formatting. At a high-level the steps we are going to do are:

  1. Reformat your commit with CDT’s new coding style
  2. Create a commit against the pre-formatted CDT that has only the files your commit changed formatted – but without your other changes

The diff between 1 and 2 above is an updated version of the diff for your real change.

Step-by-step this breaks down as:

Pre-requisites

  • Modern bash shell with sed, awk, grep, git, python, etc
    • I am using Ubuntu 18.04 LTS and python 2.7
  • Eclipse EASE with Py4J Python language support
  • Eclipse workspace setup for CDT development, follow the standard setup on the wiki and perform these extra steps:
  • Copy releng/scripts/cleanup.py somewhere outside of your gitroot so you can access it as the branches change later
  • Set ECLIPSE environment variable to path to eclipse on your machine to make some of the commands below easier to copy/paste

Step 1: Checkout the commit to rebase

First step is to checkout in CDT repo the commit you want to rebase onto current master. For example if you are updating a commit in gerrit, you could press Download in the top right and copy/paste the Checkout command:

download

Step 2: Reformat commit to new style

Start by creating a new branch to work on:

git checkout -b commit_to_rebase
Then rebase your change onto commit 35996a5c5ca, where all the per-project formatter settings have been applied, but the code has not been formatted yet. If your original commit is not too far behind this will finish without conflicts. If you have any conflicts, resolve them now.
git rebase 35996a5c5ca5c254959ba48241eaada6dbf8628d

Reformat the code to current standard using the following steps:

Step 2a: Close open editors in Eclipse

The EASE script will run on all open editors, so make sure to start with no open editors.

Step 2b: Open all the Java files modified in your commit

Using git’s diff-tree command we can get all the Java files as a list and then open them with Eclipse.
git diff-tree --no-commit-id --name-only -r commit_to_rebase -- *.java | xargs $ECLIPSE

Step 2c: Run cleanup.py

With Eclipse EASE run cleanup.py:

  1. Create a new Run Launch Configuration of type EASE Script
  2. In Script Source browse the filesystem to where you saved cleanup.py earlier
  3. Ensure Execution Engine is set to Python (Py4J)
  4. Press Run

Each open editor will have the clean up actions run, and then be closed.

Step 2d: Remove trailing whitespace in files

CDT’s code standards require trailing whitespace to be removed from all files marked with remove trailing whitespace in .gitattributes. To do this, run this bit of shell:

git show master:.gitattributes | awk '/# remove trailing whitespace/{getline; print $1}' |
    while read i ; do
        echo "Removing trailing whitespace on $i files"
        git diff-tree --no-commit-id --name-only -r commit_to_rebase -- "$i" | xargs --no-run-if-empty sed -i 's/[ \t]*$//'
    done

Step 2e: Save/commit cleanup changes

Update the change to now contain the formatted files.
git add -u
git commit --amend --reuse-message=HEAD

Step 3: Create a base commit to compare against

In this step create a commit that has only the files modified in the original commit cleaned up, but no other ones. This will be the base for the diff we create later.

Step 3a: Create a new branch

Start by checking out to a new branch the same commit as above with the formatter settings

git checkout 35996a5c5ca5c254959ba48241eaada6dbf8628d -b commit_to_format

Step 3b: Cleanup the modified files

Repeat Step 2a to Step 2d above to cleanup the files.

Step 3c: Save/commit cleanup changes

Save the files which are now formatted, but without the change you wish to rebase in a commit
git add -u
git commit -m"formatted files"

Step 4: Create a new commit that can be cherry-picked to master

Apply the change so you have a history on commit_to_format branch that is two ahead of 35996a5c5c, the first being the formatted files created in step 3, the second being the change we are trying to get onto master, which will be created now

Step 4a: Diff and apply the change

Diff the two branches we just made, that diff is the real work you are trying to get on master, and apply that diff
git diff commit_to_format..commit_to_rebase | git apply

Step 4b: Commit the change

Save the edit, reusing your original commit message (and therefore Change-Id!)
git add -u
git commit --reuse-message=commit_to_rebase

Step 5: Cherry-pick the new commit onto master

You now have a commit, marked with commit_to_format, that can be cherry-picked onto master. If other commits have made a conflicting edit since the reformat you may have some conflicts to resolve when you do this cherry-pick
git checkout master
git cherry-pick commit_to_format

Step 6: Push commit to gerrit

Push your commit now that it is ready, if you are using gerrit you can do:

git push origin master:refs/for/master

Step 7: Clean up your branches

Once you are done make sure to remove the branches you don’t need anymore.

git branch -D commit_to_rebase
git branch -D commit_to_format

All done!

And that is it. Hopefully you have now recreated your patch with just a few automated steps, instead of a painful manual copy+paste job. These instructions are also in the CDT repo in releng/scripts/rebase_helper.sh.

This set of steps shows that there are still some more automatable things that could be done. In particular being able to run Code Clean Ups from the command line in Eclipse would be really nice. Eclipse’s Java code formatter can be run from the command line.

And finally, join in on the cdt-dev mailing list!

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