Suppose I have some commits:
<sha1> bug due to function1
<sha2> bug due to function2
... other commits
and I would like to squash commits 1 and 2 together, keeping only the message of the second commit, then I would use git rebase -i, edit to:
pick <sha1> bug due to function1
squash <sha2> bug due to function2
... other commits
And I would always need to edit the combined messages and delete the first one.
I know I could rearrange the commits and use fixup like this:
pick <sha2> bug due to function2
fixup <sha1> bug due to function1
pick <sha3> other commit
but then I have the risk that, reversing the order of the two commits, there might be some conflicts.
How could I achieve the same result with less manipulations, especially avoiding the editing of the combined message. Note that there might be many commits before commit 1 and after commit 2.
Use fixup -C in the rebase todo editor. [1]
pick <sha1> bug due to function1
fixup -C <sha2> bug due to function2
... other commits
Documented in the editor session.
# 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
Note that the squash commit will get the author and timestamp from <sha1>, not from <sha2> (thanks to Johannes in the comments).