[PATCH 2/2] hooks: add signature using "interpret-trailers"

[Kaartic Sivaraam <kaarticsivaraam91196@gmail.com>]

The sample hook to prepare the commit message before
a commit allows users to opt-in to add the signature
to the commit message. The signature is added at a place
that isn't consistent with the "-s" option of "git commit".
Further, it could go out of view in certain cases.

Add the signature in a way similar to "-s" option of
"git commit" using git's interpret-trailers command.

It works well in all cases except when the user invokes
"git commit" without any arguments. In that case manually
add a new line after the first line to ensure it's consistent
with the output of "-s" option.

While at it, name the input parameters to improve readability
of script.

Signed-off-by: Kaartic Sivaraam <kaarticsivaraam91196@gmail.com>
---
 templates/hooks--prepare-commit-msg.sample | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/templates/hooks--prepare-commit-msg.sample b/templates/hooks--prepare-commit-msg.sample
index 5a638ebda..7495078cb 100755
--- a/templates/hooks--prepare-commit-msg.sample
+++ b/templates/hooks--prepare-commit-msg.sample
@@ -21,7 +21,12 @@
 # The third example adds a Signed-off-by line to the message, that can
 # still be edited.  This is rarely a good idea.
 
-sed -e '/^. Please enter the commit message /,/^#$/d' "$1" >'.sed-output.temp' && mv '.sed-output.temp' "$1"
+COMMIT_MSG_FILE=$1
+COMMIT_SOURCE=$2
+SHA1=$3
+
+SED_OUTPUT_TEMP='.sed-output-temp'
+sed -e '/^. Please enter the commit message /,/^#$/d' "$COMMIT_MSG_FILE" >"$SED_OUTPUT_TEMP" && mv "$SED_OUTPUT_TEMP" "$1"
 
 # case "$2,$3" in
 # ,|template,)
@@ -32,5 +37,14 @@ sed -e '/^. Please enter the commit message /,/^#$/d' "$1" >'.sed-output.temp' &
 #  *) ;;
 # esac
 
+# TEMP_FILE='.template-temp'
 # SOB=$(git var GIT_AUTHOR_IDENT | sed -n 's/^\(.*>\).*$/Signed-off-by: \1/p')
-# grep -qs "^$SOB" "$1" || echo "$SOB" >> "$1"
+# git interpret-trailers --in-place --trailer "$SOB" "$COMMIT_MSG_FILE"
+# if test -z "$COMMIT_SOURCE"
+# then
+#   {
+#     echo
+#     cat "$COMMIT_MSG_FILE"
+#   } >"$TEMP_FILE"
+#   mv "$TEMP_FILE" "$COMMIT_MSG_FILE"
+# fi
-- 
2.13.2.879.g2ab69f31a.dirty