Doc: improve explanation of how to use our code coverage infrastructure.

The reference to running "make coverage" in a subdirectory was a
bit obscure, so clarify what happens when you do that.  Do a little
desultory copy-editing, too.

Per a question from Peter Smith.

Discussion: https://postgr.es/m/CAHut+Pu0r3AjRSyu5E0v2-zRj8r24OSrkWs3fEBxOuaw1i8DKA@mail.gmail.com

diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index d98187c970e9de989fb595197f7ac140f7a38cea..083d0bf46b8916d49c0a765dbe3981f165f5e069 100644 (file)
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -806,12 +806,12 @@ make check PROVE_TESTS='t/001_test1.pl t/003_test3.pl'
     instrumentation, so that it becomes possible to examine which
     parts of the code are covered by the regression tests or any other
     test suite that is run with the code.  This is currently supported
-    when compiling with GCC and requires the gcov
+    when compiling with GCC, and it requires the gcov
     and lcov programs.
    
 
    
-    A typical workflow would look like this:
+    A typical workflow looks like this:
 
 ./configure --enable-coverage ... OTHER OPTIONS ...
 make
@@ -820,12 +820,11 @@ make coverage-html
 
     Then point your HTML browser
     to coverage/index.html.
-    The make commands also work in subdirectories.
    
 
    
     If you don't have lcov or prefer text output over an
-    HTML report, you can also run
+    HTML report, you can run
 
 make coverage
 
@@ -837,11 +836,23 @@ make coverage
    
 
    
-    To reset the execution counts between test runs, run:
+    You can run several different tests before making the coverage report;
+    the execution counts will accumulate.  If you want
+    to reset the execution counts between test runs, run:
 
 make coverage-clean
 
    
+
+   
+    You can run the make coverage-html or make
+    coverage command in a subdirectory if you want a coverage
+    report for only a portion of the code tree.
+   
+
+   
+    Use make distclean to clean up when done.
+