doc/todo/--metadata_fieldname__62____61__VALUE_string_comparison.mdwn

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+Thank you for `git-annex`, it's awesome!
+
+I recently figured I could add `git-annex metadata` to my research data files that contains the start and end date of timeseries data inside the files so a quick lookup by date range (”which files contain data in that time range”) is possible.
+
+This is possible when using numeric timestamps (e.g. unix timestamp like `1669981463`) but not with stringy dates (e.g. `2022-11-12T20:10:14+0200`) as `--metadata fieldname>=VALUE` does _numeric_ comparison.
+
+## Proposal: How about when `--metadata fieldname>=VALUE` falls back to string comparison when `VALUE` can't be parsed as a number?
+
+## Test case
+
+Consider this script `make-git-annex-dir-with-timestamps.sh`:
+
+```sh
+#/bin/sh
+fmt="$1";test -n "$fmt" || fmt="%FT%T%z"
+# make a new git annex repository
+d=git-annex-with-times-"$fmt";chmod +w -R "$d";rm -rf "$d";mkdir "$d";cd "$d"
+git init
+git annex init
+# create some files
+for i in `seq 1 9`;do echo "File $i" > "file$i";done
+git annex add .
+git commit -m "Add files"
+# add metadata to files
+for i in `seq 1 9`;do 
+    time_start="$(date -d"$((-20 + $i)) hours" +"$fmt")"
+    (set -x;git annex metadata --set time-start="$time_start" "file$i")
+    time_end="$(date -d"$((-10 + $i)) hours" +"$fmt")"
+    (set -x;git annex metadata --set time-end="$time_end" "file$i")
+done
+timerange_start="$(date -d "-16 hours -5 minutes" +"$fmt")"
+timerange_end="$(date -d "-12 hours +5 minutes" +"$fmt")"
+(
+set -x
+git annex find \
+    "-(" --metadata "time-start>=$timerange_start"  --and --metadata "time-start<=$timerange_end" "-)" \
+    --or \
+    "-(" --metadata "time-end>=$timerange_start"  --and --metadata "time-end<=$timerange_end" "-)"
+)
+echo "⬆⬆⬆ This should only output file4 through file8 ⬆⬆⬆"
+```
+
+Invoked with unix timestamps time format, it works as expected:
+
+```sh
+> ./make-git-annex-dir-with-timestamps.sh '%s'
+# ...
++ git annex find '-(' --metadata 'time-start>=1669923315' --and --metadata 'time-start<=1669938315' '-)' --or '-(' --metadata 'time-end>=1669923315' --and --metadata 'time-end<=1669938315' '-)'
+file4
+file5
+file6
+file7
+file8
+⬆⬆⬆ This should only output file4 through file8 ⬆⬆⬆
+```
+
+However, other stringy date formats match all files:
+
+```bash
+# typical ISO-ish time format
+> ./make-git-annex-dir-with-timestamps.sh "%FT%T%z"
+# ...
++ git annex find '-(' --metadata 'time-start>=2022-12-01T20:49:37+0100' --and --metadata 'time-start<=2022-12-02T00:59:37+0100' '-)' --or '-(' --metadata 'time-end>=2022-12-01T20:49:37+0100' --and --metadata 'time-end<=2022-12-02T00:59:37+0100' '-)'
+file1
+file2
+file3
+file4
+file5
+file6
+file7
+file8
+file9
+⬆⬆⬆ This should only output file4 through file8 ⬆⬆⬆
+```
+
+```sh
+# git-annex's own time format for 'FIELDNAME-lastchanged'
+> ./make-git-annex-dir-with-timestamps.sh "%Y-%m-%d@%H-%M-%S"
+# ...
++ git annex find '-(' --metadata 'time-start>=2022-12-01@20-38-04' --and --metadata 'time-start<=2022-12-02@00-38-04' '-)' --or '-(' --metadata 'time-end>=2022-12-01@20-38-04' --and --metadata 'time-end<=2022-12-02@00-38-04' '-)'
+file1
+file2
+file3
+file4
+file5
+file6
+file7
+file8
+file9
+⬆⬆⬆ This should only output file8 and file9 ⬆⬆⬆
+```