sanitize content of README file

Current README content is way too esoteric for someone looking at GIT
for the first time. Instead it should provide a quick summary of what
GIT is with a few pointers to other resources.

The bulk of the previous README content is moved to
Documentation/core-intro.txt.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/Makefile

@@ -71,14 +71,11 @@ doc.dep : $(wildcard *.txt) build-docdep.perl
 -include doc.dep
-git.7: README
-
-README: ../README
-	cp $< $@
+git.7 git.html: git.txt core-intro.txt
 clean:
-	rm -f *.xml *.html *.1 *.7 howto-index.txt howto/*.html doc.dep README
+	rm -f *.xml *.html *.1 *.7 howto-index.txt howto/*.html doc.dep
 %.html : %.txt
 	asciidoc -b xhtml11 -d manpage -f asciidoc.conf $<
@@ -89,8 +86,6 @@ clean:
 %.xml : %.txt
 	asciidoc -b docbook -d manpage -f asciidoc.conf $<
-git.html: git.txt README
-
 glossary.html : glossary.txt sort_glossary.pl
 	cat $< | \
 	perl sort_glossary.pl | \

Documentation/git.txt

@@ -699,7 +699,7 @@ other
 Discussion[[Discussion]]
 ------------------------
-include::README[]
+include::core-intro.txt[]
 Authors
 -------