发现git好用的比较命令git difftool_diff.tool is not configured

预留，待更新！

之前使用svn的时候，Windows上可以直接右键比较svn diff，可以像compare工具一样，手动修改差异！

在使用git时，一直使用git diff

chad@ubuntu:~/code/os-hi3559a/mpp/sample$ git diff ./Makefile
diff --git a/mpp/sample/Makefile b/mpp/sample/Makefile
index 5fbeb3c..3e1c823 100644
--- a/mpp/sample/Makefile
+++ b/mpp/sample/Makefile
@@ -4,7 +4,7 @@ all: linux lite linuxclean liteclean
 linux:
        cp ../cfg.mak.multicore ../cfg.mak
        @cd vio;     make; cp -v sample_vio ../bin/
-       @cd vdec;    make; cp -v sample_vdec ../bin/
+       @cd vdec;    make; cp -v sample_vdec ../bin/ ;cp -rv source_file ../bin/
        @cd venc;    make; cp -v sample_venc ../bin/
        @cd avs;     make; cp -v sample_avs ../bin/
        @cd fisheye; make; cp -v sample_fisheye ../bin/

chad@ubuntu:~/code/os-hi3559a/mpp/sample$ git difftool  ./Makefile

This message is displayed because 'diff.tool' is not configured.
See 'git difftool --tool-help' or 'git help config' for more details.
'git difftool' will now attempt to use one of the following tools:
meld opendiff kdiff3 tkdiff xxdiff kompare gvimdiff diffuse diffmerge ecmerge p4merge araxis bc codecompare emerge vimdiff

Viewing (1/1): 'mpp/sample/Makefile'
Launch 'meld' [Y/n]: y