Add script to ease migration to black

scripts/migrate-black.sh

@@ -0,0 +1,59 @@
+#!/bin/sh
+# check out every commit added by the current branch, blackify them,
+# and generate diffs to reconstruct the original commits, but then
+# blackified
+set -e
+
+if [ -z "$1" ]; then
+    echo Call me like
+    echo $0 name_of_your_main_branch
+    echo The main branch should be blackified already
+    exit 1
+fi
+
+BASE_BRANCH=$1
+CURRENT_BRANCH=$(git branch --show-current)
+
+if [ -z "$CURRENT_BRANCH" ] || [ "$BASE_BRANCH" = "$CURRENT_BRANCH" ]; then
+    echo You need to check out a feature branch to work on
+    exit 1
+fi
+
+if [ ! -d .git ]; then
+    echo Run me in the root of your repo
+    exit 1
+fi
+
+MERGE_BASE=$(git merge-base HEAD $BASE_BRANCH)
+
+if [ -z "$MERGE_BASE" ]; then
+    echo Could not find a common commit for current head and $BASE_BRACH
+    exit 1
+fi
+
+COMMITS_FILE=$(mktemp)
+git log --reverse --pretty='format:%H' $MERGE_BASE~1..HEAD > $COMMITS_FILE
+
+for COMMIT in $(cat $COMMITS_FILE); do
+    git checkout $COMMIT -b $COMMIT-black
+    black -q .
+    git commit -aqm 'blackify'
+done
+
+git checkout $BASE_BRANCH -b $CURRENT_BRANCH-black
+
+for COMMIT in $(cat $COMMITS_FILE); do
+    if [ -n "$LAST_COMMIT" ]; then
+        git diff $LAST_COMMIT..$COMMIT-black | patch -p1
+        git commit -aqC $COMMIT
+    fi
+    LAST_COMMIT=$COMMIT-black
+done
+
+for COMMIT in $(cat $COMMITS_FILE); do
+    git branch -qD $COMMIT-black
+done
+
+rm -rf $COMMITS_FILE
+
+git diff $BASE_BRANCH