git-submodule summary: show commit summary

This patch does the hard work to show submodule commit summary.

For a modified submodule, a series of commits will be shown with
the following command:

    git log --pretty='format:%m %s' \
        --first-parent sha1_src...sha1_dst

where the sha1_src is from the given super project commit and the
sha1_dst is from the index or working tree (switched by --cached).

For a deleted, added, or typechanged (blob<->submodule) submodule,
only one single newest commit from the existing end (for example,
src end for submodule deleted or type changed from submodule to blob)
will be shown.

If the src/dst sha1 for a submodule is missing in the submodule
directory, a warning will be issued except in two cases where the
submodule directory is deleted (type 'D') or typechanged to blob
(one case of type 'T').

In the title line for a submodule, the src/dst sha1 and the number
of commits (--first-parent) between the two commits will be shown.

The following example demonstrates most cases.

    Example: commit summary for modified submodules sm1-sm5.
    --------------------------------------------
    $ git submodule summary
    * sm1 354cd45...3f751e5 (4):
      < one line message for C
      < one line message for B
      > one line message for D
      > one line message for E

    * sm2 5c8bfb5...000000 (3):
      < one line message for F

    * sm3 354cd45...3f751e5:
      Warn: sm3 doesn't contain commit 354cd45

    * sm4 354cd34(submodule)-> 235efa(blob) (1):
      < one line message for G

    * sm5 354cd34(blob)-> 235efa(submodule) (5):
      > one line message for H

    --------------------------------------------

Signed-off-by: Ping Yin <pkufranky@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-submodule.sh

@@ -371,6 +371,108 @@ cmd_summary() {
 			echo "$name"
 		done
 	)
+
+	test -n "$modules" &&
+	git diff-index $cached --raw $head -- $modules |
+	grep -e '^:160000' -e '^:[0-7]* 160000' |
+	cut -c2- |
+	while read mod_src mod_dst sha1_src sha1_dst status name
+	do
+		if test -z "$cached" &&
+			test $sha1_dst = 0000000000000000000000000000000000000000
+		then
+			case "$mod_dst" in
+			160000)
+				sha1_dst=$(GIT_DIR="$name/.git" git rev-parse HEAD)
+				;;
+			100644 | 100755 | 120000)
+				sha1_dst=$(git hash-object $name)
+				;;
+			000000)
+				;; # removed
+			*)
+				# unexpected type
+				echo >&2 "unexpected mode $mod_dst"
+				continue ;;
+			esac
+		fi
+		missing_src=
+		missing_dst=
+
+		test $mod_src = 160000 &&
+		! GIT_DIR="$name/.git" git-rev-parse --verify $sha1_src^0 >/dev/null 2>&1 &&
+		missing_src=t
+
+		test $mod_dst = 160000 &&
+		! GIT_DIR="$name/.git" git-rev-parse --verify $sha1_dst^0 >/dev/null 2>&1 &&
+		missing_dst=t
+
+		total_commits=
+		case "$missing_src,$missing_dst" in
+		t,)
+			errmsg="  Warn: $name doesn't contain commit $sha1_src"
+			;;
+		,t)
+			errmsg="  Warn: $name doesn't contain commit $sha1_dst"
+			;;
+		t,t)
+			errmsg="  Warn: $name doesn't contain commits $sha1_src and $sha1_dst"
+			;;
+		*)
+			errmsg=
+			total_commits=$(
+			if test $mod_src = 160000 -a $mod_dst = 160000
+			then
+				range="$sha1_src...$sha1_dst"
+			elif test $mod_src = 160000
+			then
+				range=$sha1_src
+			else
+				range=$sha1_dst
+			fi
+			GIT_DIR="$name/.git" \
+			git log --pretty=oneline --first-parent $range | wc -l
+			)
+			total_commits=" ($total_commits)"
+			;;
+		esac
+
+		sha1_abbr_src=$(echo $sha1_src | cut -c1-7)
+		sha1_abbr_dst=$(echo $sha1_dst | cut -c1-7)
+		if test $status = T
+		then
+			if test $mod_dst = 160000
+			then
+				echo "* $name $sha1_abbr_src(blob)->$sha1_abbr_dst(submodule)$total_commits:"
+			else
+				echo "* $name $sha1_abbr_src(submodule)->$sha1_abbr_dst(blob)$total_commits:"
+			fi
+		else
+			echo "* $name $sha1_abbr_src...$sha1_abbr_dst$total_commits:"
+		fi
+		if test -n "$errmsg"
+		then
+			# Don't give error msg for modification whose dst is not submodule
+			# i.e. deleted or changed to blob
+			test $mod_dst = 160000 && echo "$errmsg"
+		else
+			if test $mod_src = 160000 -a $mod_dst = 160000
+			then
+				GIT_DIR="$name/.git" \
+				git log --pretty='format:  %m %s' \
+				--first-parent $sha1_src...$sha1_dst
+			elif test $mod_dst = 160000
+			then
+				GIT_DIR="$name/.git" \
+				git log --pretty='format:  > %s' -1 $sha1_dst
+			else
+				GIT_DIR="$name/.git" \
+				git log --pretty='format:  < %s' -1 $sha1_src
+			fi
+			echo
+		fi
+		echo
+	done
 }
 #
 # List all submodules, prefixed with: