Keep Porcelainish from failing by broken ident after making changes.

"empty ident not allowed" error makes commit-tree fail, so we
are already safer in that we would not end up with commit
objects that have bogus names on the author or committer fields.
However, before commit-tree is called there are already changes
made to the index file and the working tree.  The operation can
be resumed after fixing the environment problem, but when this
triggers to a newcomer with unusable gecos, the first question
becomes "what did I lose and how would I recover".

This patch modifies some Porcelainish commands to verify
GIT_COMMITTER_IDENT as soon as we know we are going to make some
commits before doing much damage to prevent confusion.

Signed-off-by: Junio C Hamano <junkio@cox.net>

git-am.sh

@@ -1,11 +1,13 @@
 #!/bin/sh
 #
-#
+# Copyright (c) 2005, 2006 Junio C Hamano
 
 USAGE='[--signoff] [--dotest=<dir>] [--utf8] [--binary] [--3way] <mbox>
   or, when resuming [--skip | --resolved]'
 . git-sh-setup
 
+git var GIT_COMMITTER_IDENT >/dev/null || exit
+
 stop_here () {
     echo "$1" >"$dotest/next"
     exit 1

git-applymbox.sh

@@ -21,6 +21,8 @@
 USAGE='[-u] [-k] [-q] [-m] (-c .dotest/<num> | mbox) [signoff]'
 . git-sh-setup
 
+git var GIT_COMMITTER_IDENT >/dev/null || exit
+
 keep_subject= query_apply= continue= utf8= resume=t
 while case "$#" in 0) break ;; esac
 do

git-merge.sh

@@ -142,6 +142,8 @@ case "$#,$common,$no_commit" in
 1,*,)
 	# We are not doing octopus, not fast forward, and have only
 	# one common.  See if it is really trivial.
+	git var GIT_COMMITTER_IDENT >/dev/null || exit
+
 	echo "Trying really trivial in-index merge..."
 	git-update-index --refresh 2>/dev/null
 	if git-read-tree --trivial -m -u $common $head "$1" &&
@@ -179,6 +181,9 @@ case "$#,$common,$no_commit" in
 	;;
 esac
 
+# We are going to make a new commit.
+git var GIT_COMMITTER_IDENT >/dev/null || exit
+
 case "$use_strategies" in
 '')
 	case "$#" in

git-resolve.sh

@@ -50,6 +50,9 @@ case "$common" in
 	;;
 esac
 
+# We are going to make a new commit.
+git var GIT_COMMITTER_IDENT >/dev/null || exit
+
 # Find an optimum merge base if there are more than one candidates.
 LF='
 '