only report git metadata for git checkout builds

.travis.yml

@@ -42,6 +42,7 @@ before_script:
  - if [[ "${CXX}" == 'clang++' ]]; then export JOBS=4; export CXX="$(which clang++)"; export CC="$(which clang)"; fi;
 
 script:
+ - rm -rf ./git
  - ./configure CXX="${CXX}" CC="${CC}" CUSTOM_CXXFLAGS="${CUSTOM_CXXFLAGS}" CUSTOM_LDFLAGS="${CUSTOM_LDFLAGS}" XML_PARSER="${XML_PARSER}" ENABLE_LOG="${ENABLE_LOG}" DEBUG="${DEBUG}" DEMO="${DEMO}" BENCHMARK="${BENCHMARK}" CPP_TESTS=True CAIRO=True FAST=True || cat config.log
  - if [[ "${DEBUG}" == True ]]; then export JOBS=$((JOBS/2)); fi;
  - make

utils/mapnik-config/build.py

@@ -79,28 +79,21 @@ dep_libs = ''.join([' -l%s' % i for i in env['LIBMAPNIK_LIBS']])
 # remove local agg from public linking
 dep_libs = dep_libs.replace('-lagg','')
 
-git_revision = 'unknown'
-git_describe = 'unknown'
-# special GIT_REVISION/GIT_DESCRIBE files present only for official releases
-# where the git directory metadata is stripped
-# more info: https://github.com/mapnik/mapnik/wiki/MapnikReleaseSteps
-revision_release_file = '../../GIT_REVISION'
-if os.path.exists(revision_release_file):
-    git_revision = open(revision_release_file,'r').read()
-else:
+git_revision = ''
+git_describe = ''
+
+try:
     git_cmd = "git rev-list --max-count=1 HEAD"
     stdin, stderr = Popen(git_cmd, shell=True, stdout=PIPE, stderr=PIPE).communicate()
     if not stderr:
         git_revision = stdin.strip()
 
-describe_release_file = '../../GIT_DESCRIBE'
-if os.path.exists(describe_release_file):
-    git_describe = open(describe_release_file,'r').read()
-else:
     git_cmd = "git describe"
     stdin, stderr = Popen(git_cmd, shell=True, stdout=PIPE, stderr=PIPE).communicate()
     if not stderr:
         git_describe = stdin.strip()
+except:
+    pass
 
 # for fonts and input plugins we should try
 # to store the relative path, if feasible