Add scripts to fetch 1 swarming log and all swarming sub-task logs.

TBR=altimin@chromium.org, scottmg@chromium.org

Change-Id: Ia91b1aacb0e761042630822acc72f86b96c1752c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2239738Reviewed-by: Fergal Daly <fergal@chromium.org>
Commit-Queue: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776906}

tools/get_swarming_logs/README.md

+# Caveat Usor
+
+This is just a quick script that I wrote and am checking in.
+Feel free to send patches and ping me if it doesn't work.

tools/get_swarming_logs/get_all.sh

+#!/bin/bash -e
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Downloads all logs from a CQ run. You can find the task ID by e.g. clicking
+# through to the CQ run from gerrit and finding, e.g. the line
+#
+# Swarming Task: 4cb6401085894f10
+#
+# This will create a .txt for the main log and create subdir for the ID and put
+# one .txt file in there for each subtask's log.
+#
+# Usage:
+#   get_all.sh <output_dir> <task ID>
+
+base_dir=$1
+shift
+id=$1
+shift
+
+bindir=$bindir
+
+function get_ids() {
+  perl -lne 'print $1 if m#shard \#0\]\(https://chromium-swarm.appspot.com/user/task/([0-9a-f]*)#;' "$1" | sort | uniq
+}
+
+log=$("$bindir"/get_one_log.sh "$base_dir" "$id")
+dir="$base_dir/$id"
+running=0
+for id in $(get_ids "$log" ); do
+  if [ "$running" -gt 32 ]; then
+    echo >&2 waiting $running
+    wait -n
+    running=$(($running - 1))
+  fi
+  echo >&2 getting $id
+  "$bindir"/get_one.sh "$dir" "$id" &
+  running=$(($running + 1))
+done
+
+while [ "$running" -gt 0 ]; do
+  echo >&2 waiting $running
+  wait -n
+  running=$(($running - 1))
+done

tools/get_swarming_logs/get_one.sh

+#!/bin/bash -ex
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Downloads all the log from a CQ run. You can find the task ID by e.g. clicking
+# through to the CQ run from gerrit and finding, e.g. the line
+#
+# Swarming Task: 4cb6401085894f10
+#
+# This will create a .txt for this log in the output dir. If you want all the
+# logs of subtasks, see get_all.sh
+#
+# Usage:
+#   get_one.sh <output_dir> <task ID>
+
+base_dir=$1
+shift
+id=$1
+shift
+
+out="$base_dir/$id.txt"
+mkdir -p "$base_dir"
+python tools/swarming_client/swarming.py \
+    collect -S chromium-swarm.appspot.com "$id" > "$out" \
+    || true
+echo "$out"