Use git worktree in the LLVM helper scripts

This commit adds a new script, llvm-env, which sets up the environment for
working with LLVM. It looks for an environment variable LLVM_ROOT and tries to
create the following hierarchy:

$LLVM_ROOT
  `- repos
  |    `- llvm
  |    `- clang
  |    `- compiler-rt
  |     [...]
  `- <branch1>
  |    `- llvm
  |    `- build
  |    `- debug
  `- <branch2>
  |    `- llvm
  |    `- build
  |    `- debug
  [...]

The $LLVM_ROOT/repos directory contains all the repositories, as checked out by
llvm-prepare, and will always track master. For other branches,
llvm-env <branch_name> will create a new directory, $LLVM_ROOT/<branch_name>,
and will add an llvm worktree directory there. If -d is passed, it will also
create a debug directory there, otherwise it will create a build directory.
Notice that these 2 can live in parallel, and we can switch between them at any
time by invoking llvm-env. It will set LLVM_SRC and LLVM_BLD accordingly, and
also modify the path to point to the binaries in LLVM_BLD.

The other scripts will now work with the LLVM_SRC and LLVM_BLD set by llvm-env
in the current shell. Because llvm-env controls whether or not we're doing a
debug build, llvm-build will no longer take a -d flag (it will instead look
after a LLVM_DEBUG environment variable, also set by llvm-env). There are
changes in llvm-projs, too, because now it no longer creates links - instead it
creates worktree directories in the corresponding $LLVM_ROOT/<branch>/llvm.
Other scripts have also been updated accordingly.

To make things easier, here are some of the changes that I had to make that are
not particularly important for the review (pretty mechanical stuff):
* Moved function has() from llvm-branch to llvm-common, so I could reuse it
* Because of this, I had to rename the has() function in llvm-projs to
has_link(), which is actually a better name for it anyway
* Disable the checks for LLVM_SRC and LLVM_BLD in llvm-common

Change-Id: I9e02f6d8e0c803e79838845013b81331dffba99c

1 files changed, 44 insertions, 0 deletions

diff --git a/helpers/.llvm-env-remove b/helpers/.llvm-env-remove
new file mode 100755
index 0000000..fba6deb
--- /dev/null
+++ b/helpers/.llvm-env-remove
@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+
+# This script removes a worktree environment for LLVM and all other projects:
+# * it removes all the worktrees and corresponding  build directories
+# * it runs git worktree prune in all the repos
+# * it DOES NOT remove the corresponding branch
+
+. llvm-common
+
+if [ "$1" = "" -o "$2" = "" ]; then
+  echo "Usage: $0 <llvm-repo-dir> <llvm-worktree-dir>"
+  exit 1
+fi
+
+llvm_repo_dir=$1
+llvm_worktree_dir=$2
+
+if [ ! -d $llvm_repo_dir ]; then
+  echo "Couldn't find llvm repo in $llvm_repo_dir"
+  exit 1
+fi
+
+if [ ! -d $llvm_worktree_dir ]; then
+  echo "Couldn't find llvm worktree in $llvm_worktree_dir"
+  exit 1
+fi
+
+# Clean up the worktrees (if we remove the LLVM worktree dir, all the other
+# worktrees are removed too, so we only need to prune the repos)
+safe_run remove_worktree $llvm_repo_dir $llvm_worktree_dir
+safe_run remove_worktree $llvm_repo_dir/../clang
+safe_run remove_worktree $llvm_repo_dir/../clang-tools-extra
+safe_run remove_worktree $llvm_repo_dir/../compiler-rt
+safe_run remove_worktree $llvm_repo_dir/../lld
+safe_run remove_worktree $llvm_repo_dir/../libcxx
+safe_run remove_worktree $llvm_repo_dir/../libcxxabi
+safe_run remove_worktree $llvm_repo_dir/../libunwind
+safe_run remove_worktree $llvm_repo_dir/../lldb
+safe_run remove_worktree $llvm_repo_dir/../test-suite
+
+# Clean up build directories too
+env_root_dir=`readlink -m $llvm_worktree_dir/../`
+echo "Removing everything in $env_root_dir"
+safe_run rm -rf $env_root_dir