Relax commit message check for URLs

CONTRIBUTING.md

@@ -1178,6 +1178,9 @@ Message](https://cbea.ms/git-commit/).
 6. Wrap the body at 72 characters.
 7. Use the body to explain what and why, not how.
 
+A body line may exceed 72 characters when everything past that column is part
+of one word containing an http or https URL, since a URL cannot be wrapped.
+
 An example (derived from Chris' blog post) looks like the following:
 ```text
 Summarize changes in around 50 characters or less

scripts/git-commit-msg.sh

@@ -149,12 +149,20 @@ if [ -n "$body" ] && [ -n "$second" ]; then
     error "separate the subject from the body with a blank line"
 fi
 
-# Rule 6.
-wide=0
+# Rule 6, except where everything past column 72 is part of one word containing
+# an http or https URL. Only the first 72 characters are searched for where that
+# word begins, because ##*[[:space:]] over the whole line is quadratic in its
+# length.
 while IFS= read -r line; do
-    [ "${#line}" -le 72 ] || wide=1
+    [ "${#line}" -gt 72 ] || continue
+    head=${line:0:72}
+    case "${head##*[[:space:]]}${line:72}" in
+        *[[:space:]]*) ;;
+        *http://?* | *https://?*) continue ;;
+    esac
+    error "body lines must not exceed 72 characters"
+    break
 done <<< "$body"
-[ "$wide" -eq 0 ] || error "body lines must not exceed 72 characters"
 
 # Rule 7, in the one form that can be decided by looking: a body that opens a
 # section announcing it is about to describe the mechanism. A regex, where the

scripts/test-git-hooks.sh

@@ -144,6 +144,50 @@ Body on the second line.
 ' 'blank line'
 expect_fail 'body over 72' 'Add a syscall
 
+This body line is quite deliberately wider than the seventy-two column limit.
+' 'exceed 72'
+for scheme in http https; do
+    expect_ok "wide $scheme URL on its own line" "Add a syscall
+
+$scheme://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
+"
+done
+for scheme in ftp git s3; do
+    expect_fail "wide $scheme URL on its own line" "Add a syscall
+
+$scheme://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
+" 'exceed 72'
+done
+expect_fail 'wide path without a scheme' 'Add a syscall
+
+www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
+' 'exceed 72'
+expect_ok 'wide https URL closing a normal message' 'Add a syscall
+
+The guest calls it during startup and stops when it gets ENOSYS back,
+so every program built against a newer libc exits before reaching main.
+
+See https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
+'
+expect_ok 'wide https URL in parentheses' 'Add a syscall
+
+See the thread (https://github.com/sysprog21/elfuse/issues/187#issuecomment-12345678).
+'
+expect_ok 'https URL starting at column 73' 'Add a syscall
+
+12345678901234567890123456789012345678901234567890123456789012345678901 https://x.y/z
+'
+expect_fail 'prose through column 72 before an https URL' 'Add a syscall
+
+123456789012345678901234567890123456789012345678901234567890123456789012 https://x.y/z
+' 'exceed 72'
+expect_fail 'prose after a wide https URL' 'Add a syscall
+
+See https://github.com/sysprog21/elfuse/issues/187#issuecomment-1234567890 here
+' 'exceed 72'
+expect_fail 'wide prose after a wide https URL' 'Add a syscall
+
+https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
 This body line is quite deliberately wider than the seventy-two column limit.
 ' 'exceed 72'
 expect_fail 'body describes how' 'Add a syscall