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Say there is a squash of 3 commits into a single commit like so:

pick abc Jan 1 stuff squash def Jan 2 stuff squash ghi Jan 3 stuff pick jkl Jan 4 stuff pick mno Jan 5 stuff

In the above, my understanding is that commits for Jan 1, 2, and 3 are squashed into a single commit. The resulting single commit is dated Jan 1 from the oldest of the 3.

Is there a way to squash in the other direction of the timestamp? Could Jan 1, 2, and 3 commits be squashed into a single commit, which is dated Jan 3?

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  • You can only squash "up". To avoid potential conflicts I typically just cherry-pick the commit I want and purposefully create an empty commit with it. Then I interactive rebase and move that commit up to the position I wish to rebase into. Here's an example where the question asked how to squash "down" into the most recent commit. Commented Jun 27 at 1:22

3 Answers 3

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5

You can reorder commits:

pick ghi Jan 3 stuff squash abc Jan 1 stuff squash def Jan 2 stuff

Git recognizes commits in the list not by their order but by commit IDs (abc, def and ghj in your example).

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If reordering the commits works without conflicts, then @phd's answer works right out.

Otherwise: you can edit the author date after the facts, by setting GIT_AUTHOR_DATE=... or by using git commit --date=....

For example:

# in the interactive rebase todo script: pick abc Jan 1 stuff squash def Jan 2 stuff squash ghi Jan 3 stuff # <- write down the hash or short hash for 'ghi' break # <- the rebase will pause here after squashing together the 3 commits pick jkl Jan 4 stuff pick mno Jan 5 stuff # save and close # when stopped after squashing: get the commit date from commit 'ghi' $ git log -1 --format="%ad" ghi $ git commit --date="<the date above>" --amend # in one go: $ git commit --date="$(git log -1 --format="%ad" ghi)" --amend # if all is to your liking: $ git rebase --continue
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You can do this non-interactively by:

  1. Calling the editor in the script to do the initial editing of commands
  2. Doing the non-interactive edits in the rest of the script

You do this with a script which you let git-rebase(1) call:

  • E.g. rebase-script
  • GIT_SEQUENCE_EDITOR=./rebase-script git rebase -i origin/main

For the non-interactive part:

  • Go through the todo list
  • Record where the last pick was (this doesn’t work with other commands)
  • Record the last squash/fixup seen
  • When you have seen the last squash/fixup: record an exec after the pick
#!/usr/bin/env bash # ./rebase-script get_commit () { set -u # arg: line line="$1" echo "$line" | cut -d' ' -f2 } process_if_previous () { set -u # arg1: prev prev="$1" # arg2: squash squash="$2" # arg3: new file new="$3" if test -n "$prev" then if test -z "$squash_commit" then return 0 fi date=$(git log --format='%ai' -1 "$squash") ed -s "$new" <<EOE /$prev a exec git commit --amend --no-edit --date="$date" . w q EOE fi } set -u # arg1: file file="$1" # First edit interactively editor=$(git var GIT_EDITOR) && "$editor" "$file" && # Now edit non-interactively new=$(mktemp) && cat "$file" >"$new" && prev="" squash_commit="" while IFS= read -r line do first="${line:0:1}" && if test "$first" = p then process_if_previous "$prev" "$squash_commit" "$new" && prev=$(get_commit "$line") && squash_commit='' elif test "$first" = s || test "$first" = f then squash_commit=$(get_commit "$line") elif test -z "$line" then # done with the todo list process_if_previous "$prev" "$squash_commit" "$new" break fi done <"$file" && cat "$new" >"$file"
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Presumably the middle way here is to manually edit the todo list, but paste in a exec git commit --amend --no-edit --date="..." line with the desired date.

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