diff --git a/proposal-template/README.md b/proposal-template/README.md
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+# Proposal template
+
+This directory will hold a template for creating new proposals, to help people
+get started.
diff --git a/proposals/README.md b/proposals/README.md
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+# Proposals
+
+This directory contains overviews for proposals that are included in this
+repository.
+
+This is analogous to [the correpsonding directory in the spec repository].
+
+[the correpsonding directory in the spec repository]: https://github.com/WebAssembly/spec/tree/master/proposals
diff --git a/repos/README.md b/repos/README.md
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+The spec and proposal repositories will be cloned in this directory by the
+make-testsuite.sh script. Don't apply local changes to these repositories, as
+the script may destroy them.
+
+This is analogous to [the coresponding wasm testsuite directory].
+
+[the coresponding wasm testsuite directory]: https://github.com/WebAssembly/testsuite/tree/master/repos
diff --git a/snapshots/README.md b/snapshots/README.md
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+# WASI Snapshots
+
+To balance between the needs of development and stability, snapshots
+represent the state of all active proposals at a moment in time. Individual
+Snapshots are stable, but WASI as a whole is evolving.
diff --git a/snapshots/make-snapshot.sh b/snapshots/make-snapshot.sh
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+++ b/snapshots/make-snapshot.sh
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+#!/bin/bash
+# Creates a snapshot based on upstream proposal repositories.
+# Derived from update-testsuite.sh in https://github.com/WebAssembly/testsuite
+set -e
+set -u
+set -o pipefail
+
+ignore_dirs=''
+
+# TODO: Add the rest.
+repos='
+  WASI
+  wasi-filesystem
+  wasi-clocks
+  wasi-random
+'
+
+log_and_run() {
+    echo ">>" $*
+    if ! $*; then
+        echo "sub-command failed: $*"
+        exit
+    fi
+}
+
+try_log_and_run() {
+    echo ">>" $*
+    $*
+}
+
+pushdir() {
+    pushd $1 >/dev/null || exit
+}
+
+popdir() {
+    popd >/dev/null || exit
+}
+
+update_repo() {
+    local repo=$1
+    pushdir repos
+        if [ -d ${repo} ]; then
+            log_and_run git -C ${repo} fetch origin
+            log_and_run git -C ${repo} reset origin/master --hard
+        else
+            log_and_run git clone https://github.com/WebAssembly/${repo}
+        fi
+
+        # Add upstream WASI as "WASI" remote.
+        if [ "${repo}" != "WASI" ]; then
+            pushdir ${repo}
+                if ! git remote | grep WASI >/dev/null; then
+                    log_and_run git remote add WASI https://github.com/WebAssembly/WASI
+                fi
+
+                log_and_run git fetch WASI
+            popdir
+        fi
+    popdir
+}
+
+merge_with_WASI() {
+    local repo=$1
+
+    [ "${repo}" == "WASI" ] && return
+
+    pushdir repos/${repo}
+        # Create and checkout "try-merge" branch.
+        if ! git branch | grep try-merge >/dev/null; then
+            log_and_run git branch try-merge origin/master
+        fi
+        log_and_run git checkout try-merge
+
+        # Attempt to merge with WASI/master.
+        log_and_run git reset origin/master --hard
+        try_log_and_run git merge -q WASI/master -m "merged"
+        if [ $? -ne 0 ]; then
+            # Ignore merge conflicts in non-test directories.
+            # We don't care about those changes.
+            try_log_and_run git checkout --ours ${ignore_dirs}
+            try_log_and_run git add ${ignore_dirs}
+            try_log_and_run git -c core.editor=true merge --continue
+            if [ $? -ne 0 ]; then
+                git merge --abort
+                popdir
+                return 1
+            fi
+        fi
+    popdir
+    return 0
+}
+
+snapshot_name=$(date --iso-8601)
+snapshot_dir=snapshots/$snapshot_name
+mkdir -p $snapshot_dir
+
+commit_message_file=$PWD/commit_message
+echo -e "Update repos\n" > $commit_message_file
+
+failed_repos=
+
+for repo in ${repos}; do
+    echo "++ updating ${repo}"
+    update_repo ${repo}
+
+    if ! merge_with_WASI ${repo}; then
+        echo -e "!! error merging ${repo}, skipping\n"
+        failed_repos="${failed_repos} ${repo}"
+        continue
+    fi
+
+    if [ "${repo}" = "WASI" ]; then
+        dest_dir=$snapshot_dir
+        log_and_run cp -r repos/${repo}/standard ${dest_dir}
+    else
+        dest_dir=$snapshot_dir/proposals/${repo}
+        mkdir -p ${dest_dir}
+
+        # Don't add tests from proposal that are the same as WASI.
+        pushdir repos/${repo}
+            for new in $(find standard -type f); do
+                old=../../repos/WASI/${new}
+                if [[ ! -f ${old} ]] || ! diff ${old} ${new} >/dev/null; then
+                    log_and_run cp ${new} ../../${dest_dir}
+                fi
+            done
+        popdir
+    fi
+
+    # Check whether any files were removed.
+    for old in $(find ${dest_dir} -type f); do
+      new=$(find repos/${repo}/standard -name ${old##*/})
+      if [[ ! -f ${new} ]]; then
+          log_and_run git rm ${old}
+      fi
+    done
+
+    # Check whether any files were updated.
+    if [ $(git status -s ${dest_dir} | wc -l) -ne 0 ]; then
+        log_and_run git add ${dest_dir}/*
+
+        repo_sha=$(git -C repos/${repo} log --max-count=1 --oneline origin/master| sed -e 's/ .*//')
+        echo "  ${repo}:" >> $commit_message_file
+        echo "    https://github.com/WebAssembly/${repo}/commit/${repo_sha}" >> $commit_message_file
+    fi
+
+    echo -e "-- ${repo}\n"
+done
+
+echo "" >> $commit_message_file
+echo "This change was automatically generated by \`make-snapshot.sh\`" >> $commit_message_file
+git commit -a -F $commit_message_file
+# git push
+
+echo "done"
+
+if [ -n "${failed_repos}" ]; then
+  echo "!! failed to update repos: ${failed_repos}"
+fi
diff --git a/standard/README.md b/standard/README.md
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+# WASI Standard
+
+In the [main WASI repository], this directory holds proposals which have
+[completed the standardization process].
+
+In a proposal repository, which is a fork of the main WASI repository,
+this directory holds the current proposal, including witx specifications,
+tests, and documentation. When the proposal is standardized, the fork is
+merged into the main repository.
+
+[main WASI repository]: https://github.com/WebAssembly/WASI/issues/360
+[completed the standardization process]: https://github.com/WebAssembly/meetings/blob/master/process/phases.md#5-the-feature-is-standardized-working-group