Using sed and filter-branch to prepend and append to Git commit messages without newlines

filter-branch-prepend-and-append

# Prepending text to the five most recent commit messages:
git filter-branch --msg-filter 'sed "s/\(.*\)/[prepended text] \1/g"' HEAD~5..HEAD

# Appending text to the five most recent commit messages:
git filter-branch --msg-filter 'sed "s/\(.*\)/\1 [appended text]/g"' HEAD~5..HEAD

Note that this prepends line by line. I.e. if you have multiline commit messages each line gets prepended the string.

Note that this prepends line by line. I.e. if you have multiline commit messages each line gets prepended the string.

# Prepending on the first line only:
git filter-branch -f --msg-filter 'sed "1 s/^/[prepended text]/g"' HEAD~5..HEAD