util/scripts/gerrit-rebase

   1 #!/usr/bin/env bash
   2 # SPDX-License-Identifier: GPL-2.0-only
   3
   4 # $0 from-branch to-branch
   5 #
   6 # applies all commits that from-branch has over to-branch,
   7 # based on a common ancestor and gerrit meta-data
   8 from=$1
   9 to=$2
  10
  11 # match string: this is the git commit line that is used to
  12 # identify commits that were already copied over.
  13 #
  14 # Must not contain spaces except for leading and trailing.
  15 #
  16 # The first pick was Change-Id, but it was lost too often,
  17 # so go for Reviewed-on instead. It's also unique because it
  18 # contains the gerrit instance's host name and the change's number
  19 # on that system.
  20 match_string='[-A-Za-z]*[Rr]eviewed-on:'
  21
  22 # Custom root: allow a certain CL (identified by matching either side's
  23 # match_string) to be the new root, instead of using git's common history only.
  24 # This allows cutting down on commits that are re-evaluated on every run.
  25 #
  26 # Use:
  27 # To the commit message of a commit on the "to" side, add
  28 # $custom_root: match_string (the part coming after $match_string)
  29 #
  30 # For a $match_string of ~ "Reviewed-on: " this might
  31 # be "$custom_root: https://example.com/12345"
  32 #
  33 # On traversal, the commit with "$match_string: https://example.com/12345"
  34 # is then considered a base commit.
  35 custom_root='^Gerrit-Rebase-Ignore-CLs-Before:'
  36
  37 # fetch common ancestor
  38 common_base=$(git merge-base ${from} ${to} 2>/dev/null)
  39
  40 if [ -z "${common_base}" ]; then
  41         echo \"${from}\" or \"${to}\" is not a valid branch name.
  42         exit 1
  43 fi
  44
  45 from_base=$common_base
  46
  47 # fetch custom root ID
  48 croot_marker=$(git log --pretty=%b -1 --grep "${custom_root}" \
  49         ${common_base}..${to} | \
  50         grep "${custom_root}" | cut -d: -f2-)
  51 if [ -n "${croot_marker}" ]; then
  52         from_base=$( ( \
  53                 git log --pretty=%H -1 \
  54                 --grep "^${match_string}${croot_marker}" \
  55                 ${from_base}..${from}; echo ${from_base} )| head -1)
  56 fi
  57
  58 # collect matches that are present on the target side
  59 to_matches="$(git log ${common_base}..${to} | \
  60         grep "^    ${match_string}" | \
  61         cut -d: -f2-)"
  62
  63 # start rebase process, but fail immediately by enforcing an invalid todo
  64 GIT_SEQUENCE_EDITOR="echo 'Ignore this error, it works around a git-rebase limitation'>" \
  65         git rebase -i --onto ${to} ${from} ${to} 2>/dev/null
  66
  67 # write new rebase todo
  68 # the appended "commit" line triggers handling of the last log entry
  69 commit=""
  70 (git log --reverse ${from_base}..${from} | \
  71         grep -E "(^commit [0-9a-f]{40}\$|^    ${match_string})"; \
  72         echo "commit") | \
  73 while read key value; do
  74         if [ "${key}" = "commit" ]; then
  75                 if [ -n "${commit}" ]; then
  76                         git log -n 1 --pretty="pick %h %s" ${commit}
  77                 fi
  78                 commit="${value}"
  79         else
  80                 # if value was already found on the "to" side, skip this
  81                 # commit
  82                 if [[ ${to_matches} == *"${value}"* ]]; then
  83                         commit=""
  84                 fi
  85         fi
  86 done | GIT_SEQUENCE_EDITOR="cat >" git rebase --edit-todo
  87
  88 # allow user to edit todo
  89 git rebase --edit-todo
  90
  91 # start processing todo to mimick git rebase -i behavior
  92 git rebase --continue