| # Monorepo History Pruning |
| |
| These are the steps we will/did follow to prune excessive history from the [flutter/engine](https://github.com/flutter/engine) repository when we merged with [flutter/flutter](https://github.com/flutter/flutter). The idea was to retain as much useful history as possible without blowing up the footprint of the framework's `.git` folder. The history that should get merged should be as relative and useful to currently engine development. |
| |
| The engine `.git` folder is ~780MB of history. |
| |
| * Binary files were checked in that are not used anymore. |
| * Third party librariers were checked in and removed nearly a decade ago. |
| * Examples were created and later moved elsewhere. |
| |
| ## Step 1: Fresh Clone + Safety |
| |
| Do not start with your working tree. |
| Remove the origin so we don't mess with the `flutter/engine`. |
| |
| ```shell |
| ############################################## |
| ## Do some cleanup work on the engine and get |
| ## the folder structure right. |
| ############################################## |
| |
| # clone the repo to a fresh working folder |
| git clone git@github.com:flutter/engine.git engine_prep |
| cd engine_prep |
| |
| # for saftey - remove the remote - we're going to edit history |
| git remote remove origin |
| ``` |
| |
| ### Optional - Analyze the repo |
| |
| If you want to analyze the repository, you should intall [git filter-repo](http://github.com/newren/git-filter-repo) on your path and then run: |
| |
| ```shell |
| # Analyze if you want, just remember to remove .git/filter-repo |
| git filter-repo --analyze --force |
| ``` |
| |
| The output is stored in `.git/filter-repo`. |
| |
| ## Step 2: Prune the History |
| |
| The following table is pulled from git-filter-repo's analsis. The `Packed Size` due to cross referencing. In general; we looked at large files that are not referenced any more and folders older than 2016. |
| |
| | Packed Size | Deleted Date | Path | Notes | |
| |-------------|:-------------|:----------------------------------------|:-----------------------------| |
| | 112784745 | 2024-05-13 | ci/licenses_golden/licenses_third_party | | |
| | 27531902 | ~2021 | *.jar | binary | |
| | 27379931 | 2016-08-09 | third_party/android_platform | android_platform and webview | |
| | 27000000 | 2024-07-15 | impeller/docs/assets/*.(png|gif) | moved to another repository | |
| | 15121375 | 2023-02-13 | *.ttc | font files | |
| | 10104182 | 2023-02-13 | */SourceHanSerifCN* | | |
| | 7985682 | 2018-08-08 | travis | old ci | |
| | 6315637 | 2015-11-07 | examples/game | | |
| | 3939429 | 2015-07-28 | sky/sdk | | |
| | 3939429 | 2015-07-28 | sky/packages/sky | | |
| | 3903787 | 2016-08-09 | mojo | | |
| | 3686830 | 2022-06-14 | testing/scenario_app/android/reports | | |
| | 3188930 | 2015-06-30 | tests/fast | | |
| | 3173966 | 2015-08-07 | */example/game* | | |
| | 2018961 | 2016-08-09 | third_party/libxml | | |
| | 1804199 | 2016-08-09 | third_party/tcmalloc | | |
| | 1393936 | ~2016 | *.dll | binary | |
| | 1373740 | 2017-07-06 | tests/data | | |
| | 1100665 | 2015-06-27 | benchmarks/parser/resources/html5.html | | |
| | 1059673 | 2015-07-20 | third_party/protobuf | | |
| | 978870 | 2022-04-27 | impeller/third_party | | |
| | 798852 | 2015-07-20 | third_party/cython | | |
| | 778560 | 2022-01-24 | lib/web_ui/test/golden_files | | |
| | 634455 | 2016-08-09 | third_party/libpng | | |
| | 610751 | 2024-05-13 | .golden | | |
| | 550475 | 2024-09-17 | impeller/fixtures/flutter_logo_baked.* | | |
| | 526837 | 2016-08-09 | third_party/libevent | | |
| | 523436 | 2015-07-20 | third_party/boringssl | | |
| | 514968 | 2022-04-27 | impeller/fixtures/image.png | | |
| | 461527 | 2015-12-11 | third_party/re2 | | |
| | 418122 | 2015-10-12 | examples/demo_launcher | | |
| | 413787 | 2015-11-07 | .aac | | |
| | 362787 | 2016-08-09 | third_party/glfw | | |
| | 349604 | 2016-08-09 | third_party/harfbuzz-ng | | |
| | 340869 | 2016-08-09 | third_party/okhttp | | |
| | 321659 | 2016-08-09 | .S | | |
| | 300824 | 2016-08-09 | .so | | |
| | 257633 | 2016-08-09 | third_party/libjpeg | | |
| | 257519 | 2016-08-09 | third_party/jinja2 | | |
| | 249618 | 2016-08-09 | third_party/zlib | | |
| | 218643 | 2015-12-11 | third_party/brotli | | |
| | 188622 | 2021-01-06 | .idl | | |
| | 184593 | 2015-09-02 | third_party/khronos | | |
| | 173210 | 2016-08-09 | .gypi | | |
| | 170484 | 2016-08-09 | third_party/expat | | |
| | 169578 | 2016-08-09 | .asm | | |
| | 161360 | 2016-08-09 | .m4 | | |
| | 142670 | 2018-05-10 | .in | | |
| | 140364 | 2015-12-11 | third_party/ots | | |
| | 137270 | 2016-08-09 | .hh | | |
| | 136787 | 2016-08-09 | .gyp | | |
| | 99503 | 2016-08-09 | third_party/qcms | | |
| | 91730 | 2015-08-21 | .pxd | | |
| | 84850 | 2016-08-09 | third_party/yasm | | |
| |
| The following command will remove files and foldes from the checkout history. Since this is a destructive edit, the SHA1 git hashes will be changed in the process. At the end, the `.git` history will be 74 MB of object files. |
| |
| ```shell |
| # Lets do some heavy filtering; |
| # .git starts out at ~780MB and ends up at ~110MB |
| git filter-repo --force --invert-paths \ |
| --path-glob 'impeller/docs/assets/*.png' \ |
| --path-glob 'impeller/docs/assets/*.gif' \ |
| --path-glob '*/example/game/*' \ |
| --path-glob 'benchmarks/parser/resources/html5.html' \ |
| --path-glob '*.dll' \ |
| --path-glob '*.jar' \ |
| --path-glob '*/SourceHanSerifCN*' \ |
| --path-glob 'third_party/txt/third_party/fonts/NotoSansCJK-Regular.ttc' \ |
| --path-glob 'impeller/fixtures/flutter_logo_baked.*' \ |
| --path-glob 'impeller/fixtures/image.png' \ |
| --path-glob '*.golden' \ |
| --path-glob '*.aac' \ |
| --path-glob '*.S' \ |
| --path-glob '*.so' \ |
| --path-glob '*.idl' \ |
| --path-glob '*.gpy' \ |
| --path-glob '*.gypi' \ |
| --path-glob '*.asm' \ |
| --path-glob '*.m4' \ |
| --path-glob '*.in' \ |
| --path-glob '*.pxd' \ |
| --path-glob '*.hh' \ |
| --path 'ci/licenses_golden/licenses_third_party' \ |
| --path 'testing/scenario_app/android/reports' \ |
| --path 'impeller/third_party' \ |
| --path 'mojo/public/third_party' \ |
| --path 'tests/data' \ |
| --path 'tests/fast' \ |
| --path 'tests/framework' \ |
| --path 'travis' \ |
| --path 'mojo' \ |
| --path 'sky/sdk' \ |
| --path 'sky/engine' \ |
| --path 'sky/tools/webkitpy' \ |
| --path 'sky/shell' \ |
| --path 'sky/packages/sky' \ |
| --path 'sky/tests' \ |
| --path 'sky/unit' \ |
| --path 'sky/services' \ |
| --path 'sky/compositor' \ |
| --path 'sky/build' \ |
| --path 'sky/specs' \ |
| --path 'skysprites' \ |
| --path 'examples/demo_launcher' \ |
| --path 'examples/game' \ |
| --path 'third_party/qcms' \ |
| --path 'third_party/libevent' \ |
| --path 'third_party/boringssl' \ |
| --path 'third_party/tcmalloc' \ |
| --path 'third_party/cython' \ |
| --path 'third_party/protobuf' \ |
| --path 'third_party/libpng' \ |
| --path 'third_party/re2' \ |
| --path 'third_party/harfbuzz-ng' \ |
| --path 'third_party/jinja2' \ |
| --path 'third_party/libjpeg' \ |
| --path 'third_party/glfw' \ |
| --path 'third_party/zlib' \ |
| --path 'third_party/android_platform' \ |
| --path 'third_party/expat' \ |
| --path 'third_party/brotli' \ |
| --path 'third_party/yasm' \ |
| --path 'third_party/khronos' \ |
| --path 'third_party/okhttp' \ |
| --path 'third_party/libxml' \ |
| --path 'third_party/ots' \ |
| --path 'third_party/libXNVCtrl' \ |
| --path 'lib/web_ui/test/golden_files' \ |
| --path 'apk' \ |
| --path 'flutter' \ |
| --path 'base' \ |
| --path 'sdk' \ |
| --path 'gpu' \ |
| --path 'engine' \ |
| --path 'tools/webkitpy' \ |
| --path 'tools/valgrind' \ |
| --path 'tools/clang' \ |
| --path 'tools/android' \ |
| --path 'build/linux' \ |
| --path 'build/win' \ |
| --path 'build/mac' \ |
| --path 'ui' \ |
| --path 'examples/stocks' \ |
| --path 'examples/stocks2' \ |
| --path 'examples/stocks-fn' \ |
| --path 'examples/data' \ |
| --path 'examples/fitness' \ |
| --path 'examples/city-list' \ |
| --path 'examples/widgets' \ |
| --path 'examples/raw' \ |
| --path 'examples/color' \ |
| --path 'examples/flights' \ |
| --path 'examples/rendering' \ |
| --path 'examples/fn' \ |
| --path 'specs' \ |
| --path 'url' \ |
| --path 'services' \ |
| --path 'framework' \ |
| --path 'crypto' \ |
| --path 'skia/ext' \ |
| --path 'e2etests' \ |
| --path 'tests/resources' \ |
| --path 'viewer' \ |
| --path 'lib/stub_ui' \ |
| --path 'content_handler' |
| |
| # Garbage collect! |
| git reflog expire --expire=now --all && git gc --prune=now --aggressive |
| ``` |
| |
| ## Step 3 - Rewirte directories |
| |
| The final destination for the engine source code will be in the directory `engine/src/flutter` *except* for `DEPS` which remains at the root. Using `git mv` only affects HEAD and can have some problems when logging. Instead we'll re-write history so it makes sense in the new world. |
| |
| ```shell |
| # Move files to engine/src/flutter, update tags so they don't collide, and move DEPS back to root. |
| git filter-repo --to-subdirectory-filter engine/src/flutter --tag-rename '':'engine-' --force |
| git filter-repo --path-rename engine/src/flutter/DEPS:DEPS |
| ``` |
| |
| ## Step 4 - Rewrite the PR links |
| |
| The PR link in the first line of the comment message will be wrong; `flutter/flutter` doesn't have the same history. To make history a little bit better, we only want to edit the first line. This must be done before we merge with the `flutter/flutter` repo so as not to step on their commit lines. |
| |
| ```shell |
| git filter-repo --force --message-callback ' |
| return re.sub(br"^(.*)\((#\d+)\)\n(.*)", br"\1(flutter/engine\2)\n\3", message, 1) |
| ' |
| ``` |
| |
| ## Execute Order 42: Merge The Repositories |
| |
| ```shell |
| ############################################## |
| ## Now handle merging into flutter/flutter |
| ############################################## |
| |
| git clone git@github.com:flutter/flutter.git flutter_merge |
| cd flutter_merge |
| |
| # add the other tree as remote |
| git remote add -f engine-upstream ~/src/engine_prep |
| |
| # --no-commit is important because we want to look around |
| git merge --no-commit --allow-unrelated-histories engine-upstream/main |
| |
| # You're a wizard, Harry |
| git commit -m "Merge flutter/engine into framework" |
| |
| # Garbage collect! |
| # Now at 234MB .git |
| git reflog expire --expire=now --all && git gc --prune=now --aggressive |
| ``` |
