Tighten comments on the home-discovery fix and CI guard

Make the rem comments in the four .bat files point directly at the line
that follows (why the trailing-backslash strip is needed) rather than
re-explaining the whole bug, and shorten the CI-step comment to what the
step does.

Signed-off-by: Craig Perkins <cwperks@amazon.com>

Author: Craig Perkins

.github/workflows/plugin_install.yml

@@ -68,15 +68,11 @@ jobs:
           jdk-version: 21
 
       - name: Verify demo config script locates OpenSearch home on Windows
-        # Regression guard for #6023: the tools/*.bat parent-directory walk used
-        # %~dpI on a path ending in "\." which does not ascend, so the script
-        # exited non-zero and OpenSearch failed to start on Windows with no
-        # error output. Run the script natively under cmd.exe (unlike the
-        # bash-invoked path in start-opensearch), with OPENSEARCH_HOME unset so
-        # the home-discovery loop is exercised. The -s flag makes an
-        # already-configured opensearch.yml a benign exit 0 (start-opensearch
-        # already ran the installer), while a home-discovery failure still
-        # exits non-zero from setBaseDir - which is exactly what we guard.
+        # Regression guard for #6023: run the demo installer natively under
+        # cmd.exe (start-opensearch invokes it via bash, which hid the bug) with
+        # OPENSEARCH_HOME unset, so the home-discovery loop must resolve it. -s
+        # makes an already-configured opensearch.yml exit 0; a discovery failure
+        # still exits non-zero.
         if: ${{ runner.os == 'Windows' }}
         shell: cmd
         run: |

tools/audit_config_migrater.bat

@@ -6,9 +6,8 @@ if defined OPENSEARCH_HOME goto find_home_done
 set "OPENSEARCH_HOME=%DIR%"
 :find_home
 if exist "%OPENSEARCH_HOME%lib\opensearch-*.jar" goto find_home_done
-rem Strip the trailing backslash before expanding the parent, otherwise
-rem %%~dpI on a path ending in "\." resolves to the same directory and the
-rem loop never ascends (breaks OpenSearch startup on Windows, silently).
+rem Strip the trailing "\" first: %%~dpI of "...\dir\." returns "...\dir\"
+rem (no ascent), so the loop would never terminate. See #6023.
 for %%I in ("%OPENSEARCH_HOME:~0,-1%") do set "PARENT=%%~dpI"
 if /I "%PARENT%" == "%OPENSEARCH_HOME%" (
   echo Could not locate OpenSearch home. Set OPENSEARCH_HOME manually. 1>&2

tools/hash.bat

@@ -6,9 +6,8 @@ if defined OPENSEARCH_HOME goto find_home_done
 set "OPENSEARCH_HOME=%DIR%"
 :find_home
 if exist "%OPENSEARCH_HOME%lib\opensearch-*.jar" goto find_home_done
-rem Strip the trailing backslash before expanding the parent, otherwise
-rem %%~dpI on a path ending in "\." resolves to the same directory and the
-rem loop never ascends (breaks OpenSearch startup on Windows, silently).
+rem Strip the trailing "\" first: %%~dpI of "...\dir\." returns "...\dir\"
+rem (no ascent), so the loop would never terminate. See #6023.
 for %%I in ("%OPENSEARCH_HOME:~0,-1%") do set "PARENT=%%~dpI"
 if /I "%PARENT%" == "%OPENSEARCH_HOME%" (
   echo Could not locate OpenSearch home. Set OPENSEARCH_HOME manually. 1>&2

tools/install_demo_configuration.bat

@@ -7,9 +7,8 @@ if defined OPENSEARCH_HOME goto find_home_done
 set "OPENSEARCH_HOME=%DIR%"
 :find_home
 if exist "%OPENSEARCH_HOME%lib\opensearch-*.jar" goto find_home_done
-rem Strip the trailing backslash before expanding the parent, otherwise
-rem %%~dpI on a path ending in "\." resolves to the same directory and the
-rem loop never ascends (breaks OpenSearch startup on Windows, silently).
+rem Strip the trailing "\" first: %%~dpI of "...\dir\." returns "...\dir\"
+rem (no ascent), so the loop would never terminate. See #6023.
 for %%I in ("%OPENSEARCH_HOME:~0,-1%") do set "PARENT=%%~dpI"
 if /I "%PARENT%" == "%OPENSEARCH_HOME%" (
   echo Could not locate OpenSearch home. Set OPENSEARCH_HOME manually. 1>&2

tools/securityadmin.bat

@@ -6,9 +6,8 @@ if defined OPENSEARCH_HOME goto find_home_done
 set "OPENSEARCH_HOME=%DIR%"
 :find_home
 if exist "%OPENSEARCH_HOME%lib\opensearch-*.jar" goto find_home_done
-rem Strip the trailing backslash before expanding the parent, otherwise
-rem %%~dpI on a path ending in "\." resolves to the same directory and the
-rem loop never ascends (breaks OpenSearch startup on Windows, silently).
+rem Strip the trailing "\" first: %%~dpI of "...\dir\." returns "...\dir\"
+rem (no ascent), so the loop would never terminate. See #6023.
 for %%I in ("%OPENSEARCH_HOME:~0,-1%") do set "PARENT=%%~dpI"
 if /I "%PARENT%" == "%OPENSEARCH_HOME%" (
   echo Could not locate OpenSearch home. Set OPENSEARCH_HOME manually. 1>&2