Evaluation of VCS merging algorithms

Requirements

Python

To install all the Python requirements, create a conda or mamba environment:

With conda:

conda env create -f environment.yml
conda activate AST

With mamba (faster https://github.com/mamba-org/mamba):

mamba env create -f environment.yml
mamba activate AST

Maven

You must use Maven version 3.9.*.

Ubuntu

sudo apt-get install -y jq
command -v curl >/dev/null || sudo apt install curl -y
curl -fsSL https://cli.github.com/packages/githubcli-archive-keyring.gpg | sudo dd of=/usr/share/keyrings/githubcli-archive-keyring.gpg \
&& sudo chmod go+r /usr/share/keyrings/githubcli-archive-keyring.gpg \
&& echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/githubcli-archive-keyring.gpg] https://cli.github.com/packages stable main" | sudo tee /etc/apt/sources.list.d/github-cli.list > /dev/null \
&& sudo apt update \
&& sudo apt install gh -y
curl -s https://packagecloud.io/install/repositories/github/git-lfs/script.deb.sh | sudo bash

MacOS

brew install jq
brew install gh

Java

You must install Java 8, 11 and 17. You must set the JAVA8_HOME, JAVA11_HOME and JAVA17_HOME environment variables to the respective Java installations.

---

Run the code

Test the stack

To test the stack, execute:

make small-test

This runs the entire code on two small repos. The output data appears in results/small/.

• results/small/result.csv: the final result

• results/small/merges/ contains all the merges.

• results/small/merges_compared/ contains all merges and indicates whether the merge results are different and thus need to be analyzed.

• results/small/merges_tested/ contains all merges that have been tested.

• results/small/result.csv contains the final result.

Perform full analysis

To run the stack on all repos:

./run_full.sh

To run the stack on all repos and also diff the merges outputs:

./run_full.sh -d

This will run the entire code on all the repos and automatically decompress the cache if cache/ does not exist. All the output data can be found in results/. The final result is found in results/result.csv. Directory results/merges contains all the merges for each repo. Directory results/merges_tested contains all the merges that have been tested.

To execute run_full.sh on multiple machines in parallel create a machine address list in machines.txt and run:

./run_multiple_machine.sh main machines.txt <project_path_on_machine>

Load the stored cache

To decompress the cache run make decompress-cache. This is done automatically in run_full.sh if cache/ does not exist.

Store the cache

To store the cache make compress-cache.

Clean Cache

To clean the cache run make clean-cache.

Clean Workspace

To cleanup the workspace:make clean

Style Checking

To run style checking run make style.

---

Code structure

Directory structure

Committed files

• run.sh -> This file executes each step of the stack.

• run_small.sh -> This file executes the stack on two repositories.

• run_full.sh -> This file executes the stack on all the repositories.

• src/ -> contains the following scripts:

  • python/ -> contains the following scripts:

    • merge_tester.py -> Main file which performs merges and evaluates all the results across all projects.

    • test_repo_heads.py -> Checks out all repos and removes all repos that fail their tests on main branch.

    • latex_output.py -> Output latex code for the resulting plots and table.

    • merge_analyzer.py -> Analyzes a merge to determine if it should be tested.

    • merges_sampler.py -> Samples merges to be tested.

    • get_repos.py -> Downloads the repos list.

    • cache_utils.py -> Contains functions to store and load the cache.

    • clean_cache_placeholders.py -> Removes all the cache placeholders.

    • repo.py -> Contains the Repo class which represents a repo.

    • split_repos.py -> Splits the repos for parallel execution.

    • write_head_hashes.py -> Writes the head hashes of all repos to a file.

    • add_jacoco_gradle.py -> Adds jacoco to gradle projects.

    • add_jacoco_maven.py -> Adds jacoco to maven projects.

  • scripts/ -> contains the following scripts:

    • run_repo_tests.sh -> Runs a repo's programmer provided tests.

    • merge_tools/ -> Contains all the merge tools scripts.

    • utils/

      • run_remotely.sh -> Runs the full stack on a remote machine.

      • run_multiple_machine.sh -> Runs the full stack on multiple remote machines.

  • src/main/java/astmergeevaluation/FindMergeCommits.java -> Finds all merge commits in a repo.

• input_data/ -> Input data, which is a list of repositories; see its README.md.

Uncommitted Files

• cache/ -> This folder is a cache for each computation. contains:

  • test_result/ -> Caches the test results for a specific commit. Used for parent testing and repo validation.

  • merge_test_results/ -> Caches the test results for specific merges. Used for merge testing. First line indicates the merge result, second line indicates the run time.

  • merge_diff_results/ -> Caches the diff results for specific merges.

• cache-small/ -> This folder is a cache for each test computation. contains:

  • test_result/ -> Caches the test results for a specific commit. Used for parent testing and repo validation.

  • merge_test_results/ -> Caches the test results for specific merges. Used for merge testing. First line indicates the merge result, second line indicates the run time.

• .workdir/ -> This folder is used for the local computations of each process and content is named by Unix process (using "$$"). If DELETE_WORKDIRS is set to false in src/python/repo.py this folder is not deleted after the computation and can be inspectedx.

• repos/ -> In this folder each repo is cloned.

• results/ -> Contains all the results for the full analysis.

• results/small/ -> Contains all the results for the small analysis.

• jars/ -> Location for the IntelliMerge and Spork jars.

Comparing merge algorithms

To investigate differences between two mergers:

• edit file src/python/select_from_results.py to reflect the differences you are interested in.
• run src/python/select_from_results.py to create a .csv database containing only the differences.
• run src/python/replay_merge.py --merges_csv CSV_FILE --idx INDEX (maybe add -test) for the index of the merge you are interested in.