Make "git reset" a builtin.

This replaces the script "git-reset.sh" with "builtin-reset.c".

A few git commands used in the script are called from the builtin also:
"ls-files" to check for unmerged files, "read-tree" for resetting
the index file in "mixed" and "hard" resets, and "update-index" to
refresh at the end in the "mixed" reset and also for the option that
gets selected paths into the index.

The reset option with paths was implemented by Johannes Schindelin.

Since the option that gets selected paths into the index is not
a "reset" like the others because it does not change the HEAD at all,
now the command is showing a warning when the "--mixed" option
is supplied for that purpose.

The following table shows the behaviour of "git reset" for
the different supported options, where X means "changing"
the HEAD, index or working tree:

reset:  --soft  --mixed  --hard  -- <paths>
HEAD       X       X        X        -
index      -       X        X        X
files      -       -        X        -

Signed-off-by: Carlos Rica <jasampler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 106 insertions, 0 deletions

diff --git a/contrib/examples/git-reset.sh b/contrib/examples/git-reset.sh
new file mode 100755
index 0000000..1dc606f
--- /dev/null
+++ b/contrib/examples/git-reset.sh
@@ -0,0 +1,106 @@
+#!/bin/sh
+#
+# Copyright (c) 2005, 2006 Linus Torvalds and Junio C Hamano
+#
+USAGE='[--mixed | --soft | --hard]  [<commit-ish>] [ [--] <paths>...]'
+SUBDIRECTORY_OK=Yes
+. git-sh-setup
+set_reflog_action "reset $*"
+require_work_tree
+
+update= reset_type=--mixed
+unset rev
+
+while case $# in 0) break ;; esac
+do
+	case "$1" in
+	--mixed | --soft | --hard)
+		reset_type="$1"
+		;;
+	--)
+		break
+		;;
+	-*)
+		usage
+		;;
+	*)
+		rev=$(git rev-parse --verify "$1") || exit
+		shift
+		break
+		;;
+	esac
+	shift
+done
+
+: ${rev=HEAD}
+rev=$(git rev-parse --verify $rev^0) || exit
+
+# Skip -- in "git reset HEAD -- foo" and "git reset -- foo".
+case "$1" in --) shift ;; esac
+
+# git reset --mixed tree [--] paths... can be used to
+# load chosen paths from the tree into the index without
+# affecting the working tree nor HEAD.
+if test $# != 0
+then
+	test "$reset_type" = "--mixed" ||
+		die "Cannot do partial $reset_type reset."
+
+	git diff-index --cached $rev -- "$@" |
+	sed -e 's/^:\([0-7][0-7]*\) [0-7][0-7]* \([0-9a-f][0-9a-f]*\) [0-9a-f][0-9a-f]* [A-Z]	\(.*\)$/\1 \2	\3/' |
+	git update-index --add --remove --index-info || exit
+	git update-index --refresh
+	exit
+fi
+
+cd_to_toplevel
+
+if test "$reset_type" = "--hard"
+then
+	update=-u
+fi
+
+# Soft reset does not touch the index file nor the working tree
+# at all, but requires them in a good order.  Other resets reset
+# the index file to the tree object we are switching to.
+if test "$reset_type" = "--soft"
+then
+	if test -f "$GIT_DIR/MERGE_HEAD" ||
+	   test "" != "$(git ls-files --unmerged)"
+	then
+		die "Cannot do a soft reset in the middle of a merge."
+	fi
+else
+	git read-tree -v --reset $update "$rev" || exit
+fi
+
+# Any resets update HEAD to the head being switched to.
+if orig=$(git rev-parse --verify HEAD 2>/dev/null)
+then
+	echo "$orig" >"$GIT_DIR/ORIG_HEAD"
+else
+	rm -f "$GIT_DIR/ORIG_HEAD"
+fi
+git update-ref -m "$GIT_REFLOG_ACTION" HEAD "$rev"
+update_ref_status=$?
+
+case "$reset_type" in
+--hard )
+	test $update_ref_status = 0 && {
+		printf "HEAD is now at "
+		GIT_PAGER= git log --max-count=1 --pretty=oneline \
+			--abbrev-commit HEAD
+	}
+	;;
+--soft )
+	;; # Nothing else to do
+--mixed )
+	# Report what has not been updated.
+	git update-index --refresh
+	;;
+esac
+
+rm -f "$GIT_DIR/MERGE_HEAD" "$GIT_DIR/rr-cache/MERGE_RR" \
+	"$GIT_DIR/SQUASH_MSG" "$GIT_DIR/MERGE_MSG"
+
+exit $update_ref_status