|
| 1 | +# Monorepo History Pruning |
| 2 | + |
| 3 | +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. |
| 4 | + |
| 5 | +The engine `.git` folder is ~780MB of history. |
| 6 | + |
| 7 | +* Binary files were checked in that are not used anymore. |
| 8 | +* Third party librariers were checked in and removed nearly a decade ago. |
| 9 | +* Examples were created and later moved elsewhere. |
| 10 | + |
| 11 | +## Step 1: Fresh Clone + Safety |
| 12 | + |
| 13 | +Do not start with your working tree. |
| 14 | +Remove the origin so we don't mess with the `flutter/engine`. |
| 15 | + |
| 16 | +```shell |
| 17 | +############################################## |
| 18 | +## Do some cleanup work on the engine and get |
| 19 | +## the folder structure right. |
| 20 | +############################################## |
| 21 | + |
| 22 | +# clone the repo to a fresh working folder |
| 23 | +git clone [email protected]:flutter/engine.git engine_prep |
| 24 | +cd engine_prep |
| 25 | + |
| 26 | +# for saftey - remove the remote - we're going to edit history |
| 27 | +git remote remove origin |
| 28 | +``` |
| 29 | + |
| 30 | +### Optional - Analyze the repo |
| 31 | + |
| 32 | +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: |
| 33 | + |
| 34 | +```shell |
| 35 | +# Analyze if you want, just remember to remove .git/filter-repo |
| 36 | +git filter-repo --analyze --force |
| 37 | +``` |
| 38 | + |
| 39 | +The output is stored in `.git/filter-repo`. |
| 40 | + |
| 41 | +## Step 2: Prune the History |
| 42 | + |
| 43 | +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. |
| 44 | + |
| 45 | +| Packed Size | Deleted Date | Path | Notes | |
| 46 | +|-------------|:-------------|:----------------------------------------|:-----------------------------| |
| 47 | +| 112784745 | 2024-05-13 | ci/licenses_golden/licenses_third_party | | |
| 48 | +| 27531902 | ~2021 | *.jar | binary | |
| 49 | +| 27379931 | 2016-08-09 | third_party/android_platform | android_platform and webview | |
| 50 | +| 27000000 | 2024-07-15 | impeller/docs/assets/*.(png|gif) | moved to another repository | |
| 51 | +| 15121375 | 2023-02-13 | *.ttc | font files | |
| 52 | +| 10104182 | 2023-02-13 | */SourceHanSerifCN* | | |
| 53 | +| 7985682 | 2018-08-08 | travis | old ci | |
| 54 | +| 6315637 | 2015-11-07 | examples/game | | |
| 55 | +| 3939429 | 2015-07-28 | sky/sdk | | |
| 56 | +| 3939429 | 2015-07-28 | sky/packages/sky | | |
| 57 | +| 3903787 | 2016-08-09 | mojo | | |
| 58 | +| 3686830 | 2022-06-14 | testing/scenario_app/android/reports | | |
| 59 | +| 3188930 | 2015-06-30 | tests/fast | | |
| 60 | +| 3173966 | 2015-08-07 | */example/game* | | |
| 61 | +| 2018961 | 2016-08-09 | third_party/libxml | | |
| 62 | +| 1804199 | 2016-08-09 | third_party/tcmalloc | | |
| 63 | +| 1393936 | ~2016 | *.dll | binary | |
| 64 | +| 1373740 | 2017-07-06 | tests/data | | |
| 65 | +| 1100665 | 2015-06-27 | benchmarks/parser/resources/html5.html | | |
| 66 | +| 1059673 | 2015-07-20 | third_party/protobuf | | |
| 67 | +| 978870 | 2022-04-27 | impeller/third_party | | |
| 68 | +| 798852 | 2015-07-20 | third_party/cython | | |
| 69 | +| 778560 | 2022-01-24 | lib/web_ui/test/golden_files | | |
| 70 | +| 634455 | 2016-08-09 | third_party/libpng | | |
| 71 | +| 610751 | 2024-05-13 | .golden | | |
| 72 | +| 550475 | 2024-09-17 | impeller/fixtures/flutter_logo_baked.* | | |
| 73 | +| 526837 | 2016-08-09 | third_party/libevent | | |
| 74 | +| 523436 | 2015-07-20 | third_party/boringssl | | |
| 75 | +| 514968 | 2022-04-27 | impeller/fixtures/image.png | | |
| 76 | +| 461527 | 2015-12-11 | third_party/re2 | | |
| 77 | +| 418122 | 2015-10-12 | examples/demo_launcher | | |
| 78 | +| 413787 | 2015-11-07 | .aac | | |
| 79 | +| 362787 | 2016-08-09 | third_party/glfw | | |
| 80 | +| 349604 | 2016-08-09 | third_party/harfbuzz-ng | | |
| 81 | +| 340869 | 2016-08-09 | third_party/okhttp | | |
| 82 | +| 321659 | 2016-08-09 | .S | | |
| 83 | +| 300824 | 2016-08-09 | .so | | |
| 84 | +| 257633 | 2016-08-09 | third_party/libjpeg | | |
| 85 | +| 257519 | 2016-08-09 | third_party/jinja2 | | |
| 86 | +| 249618 | 2016-08-09 | third_party/zlib | | |
| 87 | +| 218643 | 2015-12-11 | third_party/brotli | | |
| 88 | +| 188622 | 2021-01-06 | .idl | | |
| 89 | +| 184593 | 2015-09-02 | third_party/khronos | | |
| 90 | +| 173210 | 2016-08-09 | .gypi | | |
| 91 | +| 170484 | 2016-08-09 | third_party/expat | | |
| 92 | +| 169578 | 2016-08-09 | .asm | | |
| 93 | +| 161360 | 2016-08-09 | .m4 | | |
| 94 | +| 142670 | 2018-05-10 | .in | | |
| 95 | +| 140364 | 2015-12-11 | third_party/ots | | |
| 96 | +| 137270 | 2016-08-09 | .hh | | |
| 97 | +| 136787 | 2016-08-09 | .gyp | | |
| 98 | +| 99503 | 2016-08-09 | third_party/qcms | | |
| 99 | +| 91730 | 2015-08-21 | .pxd | | |
| 100 | +| 84850 | 2016-08-09 | third_party/yasm | | |
| 101 | + |
| 102 | +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. |
| 103 | + |
| 104 | +```shell |
| 105 | +# Lets do some heavy filtering; |
| 106 | +# .git starts out at ~780MB and ends up at ~110MB |
| 107 | +git filter-repo --force --invert-paths \ |
| 108 | +--path-glob 'impeller/docs/assets/*.png' \ |
| 109 | +--path-glob 'impeller/docs/assets/*.gif' \ |
| 110 | +--path-glob '*/example/game/*' \ |
| 111 | +--path-glob 'benchmarks/parser/resources/html5.html' \ |
| 112 | +--path-glob '*.dll' \ |
| 113 | +--path-glob '*.jar' \ |
| 114 | +--path-glob '*/SourceHanSerifCN*' \ |
| 115 | +--path-glob 'third_party/txt/third_party/fonts/NotoSansCJK-Regular.ttc' \ |
| 116 | +--path-glob 'impeller/fixtures/flutter_logo_baked.*' \ |
| 117 | +--path-glob 'impeller/fixtures/image.png' \ |
| 118 | +--path-glob '*.golden' \ |
| 119 | +--path-glob '*.aac' \ |
| 120 | +--path-glob '*.S' \ |
| 121 | +--path-glob '*.so' \ |
| 122 | +--path-glob '*.idl' \ |
| 123 | +--path-glob '*.gpy' \ |
| 124 | +--path-glob '*.gypi' \ |
| 125 | +--path-glob '*.asm' \ |
| 126 | +--path-glob '*.m4' \ |
| 127 | +--path-glob '*.in' \ |
| 128 | +--path-glob '*.pxd' \ |
| 129 | +--path-glob '*.hh' \ |
| 130 | +--path 'ci/licenses_golden/licenses_third_party' \ |
| 131 | +--path 'testing/scenario_app/android/reports' \ |
| 132 | +--path 'impeller/third_party' \ |
| 133 | +--path 'mojo/public/third_party' \ |
| 134 | +--path 'tests/data' \ |
| 135 | +--path 'tests/fast' \ |
| 136 | +--path 'tests/framework' \ |
| 137 | +--path 'travis' \ |
| 138 | +--path 'mojo' \ |
| 139 | +--path 'sky/sdk' \ |
| 140 | +--path 'sky/engine' \ |
| 141 | +--path 'sky/tools/webkitpy' \ |
| 142 | +--path 'sky/shell' \ |
| 143 | +--path 'sky/packages/sky' \ |
| 144 | +--path 'sky/tests' \ |
| 145 | +--path 'sky/unit' \ |
| 146 | +--path 'sky/services' \ |
| 147 | +--path 'sky/compositor' \ |
| 148 | +--path 'sky/build' \ |
| 149 | +--path 'sky/specs' \ |
| 150 | +--path 'skysprites' \ |
| 151 | +--path 'examples/demo_launcher' \ |
| 152 | +--path 'examples/game' \ |
| 153 | +--path 'third_party/qcms' \ |
| 154 | +--path 'third_party/libevent' \ |
| 155 | +--path 'third_party/boringssl' \ |
| 156 | +--path 'third_party/tcmalloc' \ |
| 157 | +--path 'third_party/cython' \ |
| 158 | +--path 'third_party/protobuf' \ |
| 159 | +--path 'third_party/libpng' \ |
| 160 | +--path 'third_party/re2' \ |
| 161 | +--path 'third_party/harfbuzz-ng' \ |
| 162 | +--path 'third_party/jinja2' \ |
| 163 | +--path 'third_party/libjpeg' \ |
| 164 | +--path 'third_party/glfw' \ |
| 165 | +--path 'third_party/zlib' \ |
| 166 | +--path 'third_party/android_platform' \ |
| 167 | +--path 'third_party/expat' \ |
| 168 | +--path 'third_party/brotli' \ |
| 169 | +--path 'third_party/yasm' \ |
| 170 | +--path 'third_party/khronos' \ |
| 171 | +--path 'third_party/okhttp' \ |
| 172 | +--path 'third_party/libxml' \ |
| 173 | +--path 'third_party/ots' \ |
| 174 | +--path 'third_party/libXNVCtrl' \ |
| 175 | +--path 'lib/web_ui/test/golden_files' \ |
| 176 | +--path 'apk' \ |
| 177 | +--path 'flutter' \ |
| 178 | +--path 'base' \ |
| 179 | +--path 'sdk' \ |
| 180 | +--path 'gpu' \ |
| 181 | +--path 'engine' \ |
| 182 | +--path 'tools/webkitpy' \ |
| 183 | +--path 'tools/valgrind' \ |
| 184 | +--path 'tools/clang' \ |
| 185 | +--path 'tools/android' \ |
| 186 | +--path 'build/linux' \ |
| 187 | +--path 'build/win' \ |
| 188 | +--path 'build/mac' \ |
| 189 | +--path 'ui' \ |
| 190 | +--path 'examples/stocks' \ |
| 191 | +--path 'examples/stocks2' \ |
| 192 | +--path 'examples/stocks-fn' \ |
| 193 | +--path 'examples/data' \ |
| 194 | +--path 'examples/fitness' \ |
| 195 | +--path 'examples/city-list' \ |
| 196 | +--path 'examples/widgets' \ |
| 197 | +--path 'examples/raw' \ |
| 198 | +--path 'examples/color' \ |
| 199 | +--path 'examples/flights' \ |
| 200 | +--path 'examples/rendering' \ |
| 201 | +--path 'examples/fn' \ |
| 202 | +--path 'specs' \ |
| 203 | +--path 'url' \ |
| 204 | +--path 'services' \ |
| 205 | +--path 'framework' \ |
| 206 | +--path 'crypto' \ |
| 207 | +--path 'skia/ext' \ |
| 208 | +--path 'e2etests' \ |
| 209 | +--path 'tests/resources' \ |
| 210 | +--path 'viewer' \ |
| 211 | +--path 'lib/stub_ui' \ |
| 212 | +--path 'content_handler' |
| 213 | + |
| 214 | +# Garbage collect! |
| 215 | +git reflog expire --expire=now --all && git gc --prune=now --aggressive |
| 216 | +``` |
| 217 | + |
| 218 | +## Step 3 - Rewirte directories |
| 219 | + |
| 220 | +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. |
| 221 | + |
| 222 | +```shell |
| 223 | +# Move files to engine/src/flutter, update tags so they don't collide, and move DEPS back to root. |
| 224 | +git filter-repo --to-subdirectory-filter engine/src/flutter --tag-rename '':'engine-' --force |
| 225 | +git filter-repo --path-rename engine/src/flutter/DEPS:DEPS |
| 226 | +``` |
| 227 | + |
| 228 | +## Step 4 - Rewrite the PR links |
| 229 | + |
| 230 | +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. |
| 231 | + |
| 232 | +```shell |
| 233 | +git filter-repo --force --message-callback ' |
| 234 | + return re.sub(br"^(.*)\((#\d+)\)\n(.*)", br"\1(flutter/engine\2)\n\3", message, 1) |
| 235 | + ' |
| 236 | +``` |
| 237 | + |
| 238 | +## Execute Order 42: Merge The Repositories |
| 239 | + |
| 240 | +```shell |
| 241 | +############################################## |
| 242 | +## Now handle merging into flutter/flutter |
| 243 | +############################################## |
| 244 | + |
| 245 | +git clone [email protected]:flutter/flutter.git flutter_merge |
| 246 | +cd flutter_merge |
| 247 | + |
| 248 | +# add the other tree as remote |
| 249 | +git remote add -f engine-upstream ~/src/engine_prep |
| 250 | + |
| 251 | +# --no-commit is important because we want to look around |
| 252 | +git merge --no-commit --allow-unrelated-histories engine-upstream/main |
| 253 | + |
| 254 | +# You're a wizard, Harry |
| 255 | +git commit -m "Merge flutter/engine into framework" |
| 256 | + |
| 257 | +# Garbage collect! |
| 258 | +# Now at 234MB .git |
| 259 | +git reflog expire --expire=now --all && git gc --prune=now --aggressive |
| 260 | +``` |
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