please.sh: add a helper to work with Coverity

Coverity is a pretty complete static analysis tool. Working with it is a
bit tricky, as a so-called "Self-Scan" tool needs to be downloaded, and a
full build needs to be run through that tool, the output needs to be
packages into a .tar file and uploaded, queing work for the server side of
Coverity.

To make it simpler to use, let's pour all of our knowledge about the
Coverity process into Git for Windows' administrative script, both to
document it and to make it easier to use.

So now you only need to set the config variables coverity.username and
coverity.token and then you can call

	/usr/src/build-extra/please.sh submit_build_to_coverity \
		--worktree=. HEAD

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

please.sh

@@ -1878,6 +1878,124 @@ EOF
 	fi
 }
 
+# <coverity-token>
+init_or_update_coverity_tool () {
+	# check once per week whether there is a new version
+	coverity_tool=.git/coverity-tool
+	test ! -d $coverity_tool ||
+	test $(($(date +%s)-$(stat -c %Y $coverity_tool))) \
+		-gt $((7*24*60*60)) || return 0
+	echo "Downloading current Coverity Scan Self-Build tool" >&2
+	if test -f .git/coverity_tool.zip
+	then
+		timecond=.git/coverity_tool.zip
+	else
+		timecond="19700101 +0000"
+	fi
+	curl --form "token=$1" \
+		--form "project=git-for-windows" \
+		--time-cond "$timecond" \
+		-o .git/coverity_tool.zip.new \
+		https://scan.coverity.com/download/win64 &&
+	test -f .git/coverity_tool.zip.new || {
+		echo "Nothing downloaded; will try again in another week" >&2
+		touch $coverity_tool
+		return
+	}
+											mv -f .git/coverity_tool.zip.new .git/coverity_tool.zip ||
+	die "Could not overwrite coverity_tool.zip"
+
+	mkdir $coverity_tool.new &&
+	(cd $coverity_tool.new &&
+	 unzip ../coverity_tool.zip) ||
+	die "Could not unpack coverity_tool.zip"
+											rm -rf $coverity_tool &&
+	mv $coverity_tool.new $coverity_tool ||
+	die "Could not switch to new Coverity tool version"
+}
+
+submit_build_to_coverity () { # [--worktree=<dir>] <upstream-branch-or-tag>
+	git_src_dir="$sdk64/usr/src/MINGW-packages/mingw-w64-git/src/git"
+	while case "$1" in
+	--worktree=*)
+		git_src_dir=${1#*=}
+		test -d "$git_src_dir" ||
+		die "Worktree does not exist: %s\n" "$git_src_dir"
+		git rev-parse -q --verify e83c5163316f89bfbde7d ||
+		die "Does not appear to be a Git checkout: %s\n" "$git_src_dir"
+		;;
+	-*) die "Unknown option: %s\n" "$1";;
+	*) break;;
+	esac; do shift; done
+	test $# = 1 ||
+	die "Expected 1 argument, got $#: %s\n" "$*"
+	branch="$1"
+
+	coverity_username="$(git config coverity.username)"
+	test -n "$coverity_username" ||
+	die "Need a username to access Coverity's services\n"
+
+	coverity_token="$(git config coverity.token)"
+	test -n "$coverity_token" ||
+	die "Need a token to access Coverity's services\n"
+
+	ensure_valid_login_shell 64 ||
+	die "Could not ensure valid login shell\n"
+
+	sdk="$sdk64"
+
+	build_extra_dir="$sdk64/usr/src/build-extra"
+	(cd "$build_extra_dir" &&
+	 sdk= pkgpath=$PWD ff_master) ||
+	die "Could not update build-extra\n"
+
+	require_git_src_dir
+
+	(cd "$git_src_dir" &&
+	 case "$branch" in
+	 git-for-windows/*|v[1-9]*.windows.[1-9]*)
+		require_remote git-for-windows \
+			https://github.com/git-for-windows/git
+		case "$branch" in git-for-windows/refs/pull/[0-9]*)
+			git fetch git-for-windows \
+			    "${branch#git-for-windows/}:refs/remotes/$branch" ||
+			die "Could not fetch %s from git-for-windows\n" \
+				"${branch#git-for-windows/}"
+			;;
+		esac
+		;;
+	 upstream/*|v[1-9]*)
+		require_remote upstream https://github.com/git/git
+		case "$branch" in upstream/refs/pull/[0-9]*)
+			git fetch upstream "${branch#upstream/}:refs/remotes/$branch" ||
+			die "Could not fetch %s from upstream\n" \
+				"${branch#upstream/}"
+			;;
+		esac
+		;;
+	 esac &&
+	 git checkout -f "$branch" &&
+	 git reset --hard &&
+	 init_or_update_coverity_tool "$coverity_token" &&
+	 coverity_bin_dir=$(echo $PWD/$coverity_tool/*/bin) &&
+	 if ! test -x "$coverity_bin_dir/cov-build.exe"
+	 then
+		die "Unusable Coverity bin/ directory: '%s'\n" \
+			"$coverity_bin_dir"
+	 fi &&
+	 PATH="$coverity_bin_dir:$PATH" &&
+	 cov-build --dir cov-int \
+		make -j15 DEVELOPER=1 CPPFLAGS=-DFLEX_ARRAY=65536 &&
+	 tar caf git-for-windows.lzma cov-int &&
+	 curl --form token="$coverity_token" \
+		--form email="$coverity_username" \
+		--form file=@git-for-windows.lzma \
+		--form version="$(git rev-parse HEAD)" \
+		--form version="$(date +%Y-%m-%s-%H-%M-%S)" \
+		https://scan.coverity.com/builds?project=git-for-windows) ||
+	die "Could not submit build to Coverity\n"
+}
+
 tag_git () { #
 	sdk="$sdk64" require w3m