Use git tools instead of cogito for getting the build ID

The build ID now includes both last tagged version, commit generation
since last tagged version, as well as the leading characters of the
commit ID and a flag for dirty working tree.
(cherry picked from commit c2a0d3b)

Makefile.config.in

@@ -54,7 +54,7 @@ ASCIIDOC_FLAGS = @ASCIIDOC_FLAGS@
 AWK = @AWK@
 CATALOGS = @CATALOGS@
 CC = @CC@
-CG_COMMIT_ID = @CG_COMMIT_ID@
+GIT = @GIT@
 CONFDIR = @CONFDIR@
 DOXYGEN = @DOXYGEN@
 GLIBC21 = @GLIBC21@

configure.in

@@ -61,7 +61,7 @@ AC_PATH_PROGS(AWK, "$AWK")
 AC_PROG_RANLIB
 AC_PROG_INSTALL
 
-AC_PATH_PROGS(CG_COMMIT_ID, "cg-commit-id")
+AC_PATH_PROGS(GIT, "git")
 AC_PATH_PROGS(SPARSE, "sparse")
 
 CONFIG_ASCIIDOC="no"

src/Makefile

@@ -28,8 +28,10 @@ SUBDIRS = \
  viewer
 
 # Get the GIT HEAD ID if possible
-ifdef CG_COMMIT_ID
-BUILD_ID=$(shell GIT_DIR=$(top_srcdir)/.git $(CG_COMMIT_ID) 2> /dev/null)
+ifdef GIT
+GITDESC  = $(shell $(GIT) --git-dir=$(top_srcdir)/.git describe 2>/dev/null)
+WTDIRTY  = $(shell $(GIT) --git-dir=$(top_srcdir)/.git diff-index HEAD 2>/dev/null)
+BUILD_ID = $(subst elinks-,,$(GITDESC))$(if $(WTDIRTY),-dirty)
 endif
 INCLUDES += -DBUILD_ID="\"$(BUILD_ID)\""