add a tool to migrate tags from files to dirs

This is more conflict resistant than the old encoding where tags was a
file with a line per tag.

src/issue.rs

@@ -137,12 +137,7 @@ impl Issue {
                 } else if file_name == "dependencies" && direntry.metadata()?.is_dir() {
                     dependencies = Self::read_dependencies(&direntry.path())?;
                 } else if file_name == "tags" {
-                    let contents = std::fs::read_to_string(direntry.path())?;
+                    tags = Self::read_tags(&direntry)?;
-                    tags = contents
-                        .lines()
-                        .filter(|s| s.len() > 0)
-                        .map(|tag| String::from(tag.trim()))
-                        .collect();
                 } else if file_name == "comments" && direntry.metadata()?.is_dir() {
                     Self::read_comments(&mut comments, &direntry.path())?;
                 } else {
@@ -217,6 +212,23 @@ impl Issue {
         Ok(dependencies)
     }
 
+    fn read_tags(tags_direntry: &std::fs::DirEntry) -> Result<Vec<String>, IssueError> {
+        if !tags_direntry.metadata()?.is_dir() {
+            eprintln!("issue has old-style tags file");
+            return Err(IssueError::StdIoError(std::io::Error::from(
+                std::io::ErrorKind::NotADirectory,
+            )));
+        }
+        let mut tags = Vec::<String>::new();
+        for direntry in tags_direntry.path().read_dir()? {
+            if let Ok(direntry) = direntry {
+                tags.push(String::from(direntry.file_name().to_string_lossy()));
+            }
+        }
+        tags.sort();
+        Ok(tags)
+    }
+
     /// Add a new Comment to the Issue.  Commits.
     pub fn add_comment(
         &mut self,

tools/update-tags-encoding

@@ -0,0 +1,35 @@
+#!/bin/bash
+#
+# Check out the `entomologist-data` branch in a temporary worktree.
+# For each issue with a `tags` file:
+#     read
+
+set -e
+#set -x
+
+WORKTREE_DIR=$(mktemp --directory)
+git worktree add "${WORKTREE_DIR}" entomologist-data
+pushd "${WORKTREE_DIR}" > /dev/null
+
+for ISSUE_ID in $(find . -maxdepth 1 -type d -regextype posix-extended -regex '\./[0-9a-f]{32}'); do
+    if ! [[ -f "${ISSUE_ID}/tags" ]]; then
+        continue
+    fi
+
+    pushd "${ISSUE_ID}" > /dev/null
+
+    echo "${ISSUE_ID} has tags:"
+    TAGS=$(cat tags)
+    git rm tags
+    mkdir tags
+    for TAG in ${TAGS}; do
+        touch "tags/${TAG}"
+    done
+    git add tags
+    #git commit -m "issue ${ISSUE_ID}: update tags to new format"
+
+    popd > /dev/null
+done
+
+popd > /dev/null
+git worktree remove "${WORKTREE_DIR}"