Git: Remove GitCommand

Use VCSBase::Command instead.

Change-Id: I819e61c2fdf705717709f49ea42ad822d25300fb
Reviewed-on: http://codereview.qt-project.org/6079
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>

src/plugins/git/git.pro

@@ -20,7 +20,6 @@ HEADERS += gitplugin.h \
     gitsettings.h \
     branchdialog.h \
     branchmodel.h \
-    gitcommand.h \
     clonewizard.h \
     clonewizardpage.h \
     stashdialog.h \
@@ -42,7 +41,6 @@ SOURCES += gitplugin.cpp \
     gitsettings.cpp \
     branchdialog.cpp \
     branchmodel.cpp \
-    gitcommand.cpp \
     clonewizard.cpp \
     clonewizardpage.cpp \
     stashdialog.cpp \