Conflict when squashing linear commit history

Question

How is it possible that when trying to squash/fixup a linear branch I still have to do manual merges? The repo has been converted from Subversion. Every conflict is either "Automatic cherry-pick failed" or "Aborting commit due to empty commit message". The latter I could understand, but a --fixup-empty or something would be useful.

Typical output:

user@machine:/path (master|REBASE-i)$ git add * && git rebase --continue 
[detached HEAD c536940] fixup!
 Author: John Doe <[email protected]>
 2 files changed, 57 insertions(+), 4 deletions(-)
Automatic cherry-pick failed.  After resolving the conflicts,
mark the corrected paths with 'git add <paths>', and
run 'git rebase --continue'
Could not apply 8854a54... >6d5f180 foo
user@machine:/path (master|REBASE-i)$ git st
# Not currently on any branch.
# Unmerged paths:
#   (use "git reset HEAD <file>..." to unstage)
#   (use "git add/rm <file>..." as appropriate to mark resolution)
#
#   both modified:      filename.ics
#
no changes added to commit (use "git add" and/or "git commit -a")

Answer 1

These work:

git mergetool
git rebase --continue

Answer 2

Here's my suggestion for achieving your idea of having some kind of --fixup-empty functionality:

git filter-branch --msg-filter "sed 's/^$/Unknown/'"

This replaces empty commit messages with 'Unknown' and is particularly useful if you want to do a rebase after using git-svn to convert a Subversion repository that had some empty commit messages but can't because it fails with "Aborting commit due to empty commit message".