Context

We were rewriting ~30 lines of code, supported by tests. To do so, we disabled the tests for that code and deleted the 30 lines of code (leaving an empty method and a handful of disabled tests). One test at a time, we enabled the test and wrote the code to pass the test. Then, we committed to git.

Since the code was technically broken at each commit (the disabled tests represented missing behavior), we did not want to push our changes as-is.

When the rewrite was finished (and all tests were enabled and passing), we were ready to think about pushing our code. Instead of pushing broken commits, we chose to squash the commits into one single commit, review it as a single commit, and then commit and push following our regular process.

This post describes the squash, in case we (or you) want to repeat it.

Here’s out git log before we started the squash:


*       a65f9096b 👥 Our Team [3 hours ago] WIP - To Be Squashed
*       111b88098 👥 Our Team [3 hours ago] WIP - To Be Squashed
*       822f1598b 👥 Our Team [3 hours ago] WIP - To Be Squashed
*       df494ccbb 👥 Our Team [4 hours ago] WIP - To Be Squashed
*       537a4b4cc 👥 Our Team [4 hours ago] WIP - To Be Squashed
*       39abaa97e 👥 Our Team [4 hours ago] WIP - To Be Squashed
*       9a92a6ed0 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       f4a1d0f1a 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       bbee46810 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       397bba973 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       2f44cd9ec 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       e8b1b50d0 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       65ebc02ad 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       752ddf1b2 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       2318eaab4 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       4338ef173 👥 Our Team [5 hours ago] WIP - To Be Squashed
*       fbc7f8c03 👥 Our Team [23 hours ago] WIP - To Be Squashed
*       d67b88ce3 👥 Our Team [23 hours ago] WIP - To Be Squashed
*       b523773c1 👥 Our Team [23 hours ago] WIP - To Be Squashed
*       7b13cb1d8 👥 Our Team [23 hours ago] WIP - To Be Squashed
*       6d13d3801 👥 Our Team [23 hours ago] WIP - To Be Squashed
*       e4ccb2783 👥 Our Team [23 hours ago] WIP - To Be Squashed
*       b02247c9f 👥 Our Team [24 hours ago] WIP - To Be Squashed
*       5336a7275 👥 Our Team [24 hours ago] WIP - To Be Squashed
*       10f466ac5 👥 Our Team [24 hours ago] WIP - To Be Squashed
*       512201561 👥 Our Team [24 hours ago] WIP - To Be Squashed
*       13ddbb6c4 👥 Our Team [24 hours ago] WIP - To Be Squashed
*       2a5ab91a3 👥 Our Team [25 hours ago] R - Moved deprecated methods below non-deprecated methods.
*       2810574d5 👥 Our Team [28 hours ago] (origin/master, origin/HEAD) R- Encapsulate the foobar and the whatsit methods
*       9447c3891 👥 Our Team [28 hours ago] r - move all whizbang services into a new service subdirectory
*       c89f46071 👥 Our Team [28 hours ago] r - rename whizbang.models.ts to whizbang.ts

Interactive rebase back to the last clean commit:


git rebase -i 2a5ab91a3

This opens up a new editor window:


pick 14ddbb12c WIP - To Be Squashed
pick 512201563 WIP - To Be Squashed
pick 0f47f6ac5 WIP - To Be Squashed
pick 5336a7276 WIP - To Be Squashed
pick 02247c10f WIP - To Be Squashed
pick e4ccb2784 WIP - To Be Squashed
pick d14db3801 WIP - To Be Squashed
pick b14ccb1d8 WIP - To Be Squashed
pick 523773c11 WIP - To Be Squashed
pick d67b89ce3 WIP - To Be Squashed
pick fbc7f9c03 WIP - To Be Squashed
pick 4338ef174 WIP - To Be Squashed
pick 2318eaab5 WIP - To Be Squashed
pick 52ddf11b2 WIP - To Be Squashed
pick 5ebc013ad WIP - To Be Squashed
pick 8b11b50d0 WIP - To Be Squashed
pick 2f45cd9ec WIP - To Be Squashed
pick 397bba974 WIP - To Be Squashed
pick bbee46810 WIP - To Be Squashed
pick 4a11d0f1a WIP - To Be Squashed
pick 9a93a6ed0 WIP - To Be Squashed
pick 39abaa98e WIP - To Be Squashed
pick 537a5b4cc WIP - To Be Squashed
pick df494ccbb WIP - To Be Squashed
pick d12c7549d WIP - To Be Squashed
pick 822f1599b WIP - To Be Squashed
pick 111b88099 WIP - To Be Squashed
pick a64f9097b WIP - To Be Squashed
pick f63d58430 WIP - To Be Squashed

# Rebase 2a5ab91a3..f62d58425 onto 2a5ab91a3 (29 commands)
#
# Commands:
# p, pick <commit> = use commit
# r, reword <commit> = use commit, but edit the commit message
# e, edit <commit> = use commit, but stop for amending
# s, squash <commit> = use commit, but meld into previous commit
# f, fixup [-C | -c] <commit> = like "squash" but keep only the previous
#                    commit's log message, unless -C is used, in which case
#                    keep only this commit's message; -c is same as -C but
#                    opens the editor
# x, exec <command> = run command (the rest of the line) using shell
# b, break = stop here (continue rebase later with 'git rebase --continue')
# d, drop <commit> = remove commit
# l, label <label> = label current HEAD with a name
# t, reset <label> = reset HEAD to a label
# m, merge [-C <commit> | -c <commit>] <label> [# <oneline>]
#         create a merge commit using the original merge commit's
#         message (or the oneline, if no original merge commit was
#         specified); use -c <commit> to reword the commit message
# u, update-ref <ref> = track a placeholder for the <ref> to be updated
#                       to this position in the new commits. The <ref> is
#                       updated at the end of the rebase
#
# These lines can be re-ordered; they are executed from top to bottom.
#
# If you remove a line here THAT COMMIT WILL BE LOST.
#
# However, if you remove everything, the rebase will be aborted.
#

Next change the lines from “pick” to “squash” except for the first line - that one stays as pick as there needs to be a commit to squash to.


pick 13ddbb7c4 WIP - To Be Squashed
squash 512201561 WIP - To Be Squashed
squash 1f42f6ac6 WIP - To Be Squashed
squash 5335a7273 WIP - To Be Squashed
(etc.)

Then we save the file and git performs the rebase. (It shows Rebasing (8/29).) Afterward, we’re prompted to enter a new commit message, and we put something temporary (we will update the commit shortly).

Then, our git log looks like this. Notice that master has a single commit on top of the last clean commit. We left a “placeholder” branch at the end of our “wip” commits so we could see the before and after. When we diffed master and placeholder, they were identical, which told us the squash was successful: all the same changes, but in a single commit instead of many.


*       b78d20d66 👥 Our Team [25 hours ago] (HEAD -> master) something temporary
| *     f63d58430 👥 Our Team [3 hours ago] (placeholder) WIP - To Be Squashed
| *     a64f9097b 👥 Our Team [3 hours ago] WIP - To Be Squashed
| *     111b88099 👥 Our Team [3 hours ago] WIP - To Be Squashed
| *     822f1599b 👥 Our Team [4 hours ago] WIP - To Be Squashed
| *     4d12c7549 👥 Our Team [4 hours ago] WIP - To Be Squashed
| *     df494ccbb 👥 Our Team [10 hours ago] WIP - To Be Squashed
| *     537a5b4cc 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     39abaa98e 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     9a93a6ed0 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     f4a11d0f1 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     bbee46810 👥 Our Team [10 hours ago] WIP - To Be Squashed
| *     397bba974 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     2f45cd9ec 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     e8b11b50d 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     65ebc013a 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     752ddf11b 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     2318eaab5 👥 Our Team [5 hours ago] WIP - To Be Squashed
| *     4338ef174 👥 Our Team [6 hours ago] WIP - To Be Squashed
| *     fbc7f9c03 👥 Our Team [23 hours ago] WIP - To Be Squashed
| *     d67b89ce3 👥 Our Team [23 hours ago] WIP - To Be Squashed
| *     b523773c1 👥 Our Team [24 hours ago] WIP - To Be Squashed
| *     7b14ccb1d 👥 Our Team [24 hours ago] WIP - To Be Squashed
| *     6d14db380 👥 Our Team [24 hours ago] WIP - To Be Squashed
| *     e4ccb2784 👥 Our Team [24 hours ago] WIP - To Be Squashed
| *     b02247c10 👥 Our Team [24 hours ago] WIP - To Be Squashed
| *     5336a7276 👥 Our Team [24 hours ago] WIP - To Be Squashed
| *     10f47f6ac 👥 Our Team [24 hours ago] WIP - To Be Squashed
| *     512201561 👥 Our Team [29 hours ago] WIP - To Be Squashed
| *     13ddbb7c4 👥 Our Team [25 hours ago] WIP - To Be Squashed
|/
*       2a5ab91a3 👥 Our Team [25 hours ago] R - Moved deprecated methods below non-deprecated methods.
*       2810574d5 👥 Our Team [28 hours ago] (origin/master, origin/HEAD) R- Encapsulate the foobar and the whatsit methods
*       9447c3891 👥 Our Team [28 hours ago] r - move all whizbang services into a new service subdirectory
*       c89f46071 👥 Our Team [28 hours ago] r - rename whizbang.models.ts to whizbang.ts

Finally, we reset that commit so we could review the diff of all the squash and commit using our normal commit process.


git reset --soft HEAD^

Now we see a diff showing the combination of all of our WIP commits.