add a tools directory including a "done-last-week" script

This script lists issues that were marked `Done` between "midnight at
the start of the second most recent Monday" and "midnight at the start
of the most recent Monday".

    $ ./tools/done-last-week
    Done:
    8c73c9fd5bc4f551ee5069035ae6e866       migrate the Todo list into entomologist
    75cefad80aacbf23fc7b9c24a75aa236  🗨️ 4  # implement `ent comment ISSUE [DESCRIPTION]` (👉 seb)
    7da3bd5b72de0a05936b094db5d24304  🗨️ 1  implement `ent edit ${COMMENT}` (👉 seb)
    198a7d56a19f0579fbc04f2ee9cc234f       fix ignoring unknown file in issues directory: "README.md"
    e089400e8a9e11fe9bf10d50b2f889d7       add `ent sync` to keep local `entomologist-data` branch in sync with remote
    a26da230276d317e85f9fcca41c19d2e       `ent edit ${ISSUE}` with no change fails (👉 seb)
    317ea8ccac1d414cde55771321bdec30  🗨️ 2  allow multiple read-only ent processes simultaneously (👉 seb)
    da435e5e298b28dc223f9dcfe62a9140       add user control over state transitions (👉 lex)
    fd81241f795333b64e7911cfb1b57c8f       commit messages in the `entomologist-data` branch could be better (👉 seb)
    093e87e8049b93bfa2d8fcd544cae75f       add optional 'assignee' to issue (👉 seb)
    793bda8b9726b0336d97e856895907f8       `ent list` should have a consistent sort order (👉 seb)
    af53c561b36e9b2709b939f81daee534       use git author info to attribute issues and comments to people (👉 seb)
    9e69a30ad6965d7488514584c97ac63c       teach `ent list FILTER` to filter by assignee (👉 seb)
    a5ac277614ea4d13f78031abb25ea7d6       `ent new` and `ent comment`: detect empty issue descriptions & comments (👉 seb)
    7d2d236668872cf11f167ac0462f8751  🗨️ 1  add `ent tag ISSUE [[-]TAG]` (👉 seb)
    54f0eb67b05aa10763c86869ce840f33       `ent sync` should report what changes got fetched & what changes will be pushed (👉 seb)
    4e314a8590864fa76d22758e1785ae35       don't spawn an editor if stdin & stdout aren't a terminal (👉 seb)
    d3a705245bd69aa56524b80b5ae0bc26  🗨️ 1  move IssuesDatabase out of binary and into library (👉 sigil-03)

tools/set-done-time

@@ -0,0 +1,19 @@
+#!/bin/bash
+#
+# This script finds all issues with state=Done which do not have a
+# `done_time`.
+#
+# It sets each issue's `done_time` to the most recent time that the
+# `state` was updated from the git log.
+#
+
+set -e
+
+for ISSUE_ID in $(ent list state=done done-time=9999-01-01T00:00:00-06:00.. | grep '  ' | cut -f 1 -d ' '); do
+    echo ${ISSUE_ID}
+    UTIME=$(PAGER='' git log -n1 --pretty=format:%at%n entomologist-data -- ${ISSUE_ID}/state)
+    echo ${UTIME}
+    DATETIME=$(date --rfc-3339=seconds --date="@${UTIME}")
+    echo ${DATETIME}
+    ent done-time ${ISSUE_ID} "${DATETIME}"
+done