use markdown syntax for imagesHEADmain

Now they render right on non-Github forges.

2 files changed, 3 insertions, 2 deletions

diff --git a/README.md b/README.md
index 707f25c..1be62d4 100644
--- a/README.md
+++ b/README.md
@@ -25,7 +25,7 @@ make linux  # replace with 'macosx', etc. depending on your OS
 src/teliva hanoi.tlv
 ```
 
-<img alt='screenshot of Teliva running the Towers of Hanoi' src='doc/hanoi.png'>
+![screenshot of Teliva running the Towers of Hanoi](doc/hanoi.png)
 
 No matter what app you run, you are always guaranteed access to a single
 obvious, consistent way (currently the hotkey `ctrl-u`) to inspect its
@@ -35,7 +35,7 @@ When you look under the hood of an app, the first thing you see is a
 _big-picture view_ which shows the app's major data structures and a top-down
 view of the app's code.
 
-<img alt='screenshot of big-picture view for the Towers of Hanoi' src='doc/hanoi-big-picture.png'>
+![screenshot of big-picture view for the Towers of Hanoi](doc/hanoi-big-picture.png)
 
 Select a definition, make a change, hit `ctrl-x`, and the app will run with
 your updates. ([video](https://archive.org/details/akkartik-2021-11-14))
diff --git a/src/file.lua b/src/file.lua
index 372d49b..95ed266 100644
--- a/src/file.lua
+++ b/src/file.lua
@@ -94,6 +94,7 @@ function temporary_filename_in_same_volume(filename)
       -- file doesn't exist yet; create a placeholder and return it
       local handle = io.open(temporary_filename, 'w')
       if handle == nil then
+        -- HERE: if an app doesn't have permissions, attempts to write to disk eventually get here
         error("this is unexpected; I can't create temporary files..")
       end
       handle:close()