[PATCH 1/1] contrib: add coverage-diff script

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <dstolee@microsoft.com>

We have coverage targets in our Makefile for using gcov to display line
coverage based on our test suite. The way I like to do it is to run:

    make coverage-test
    make coverage-report

This leaves the repo in a state where every X.c file that was covered has
an X.c.gcov file containing the coverage counts for every line, and "#####"
at every uncovered line.

There have been a few bugs in recent patches what would have been caught
if the test suite covered those blocks (including a few of mine). I want
to work towards a "sensible" amount of coverage on new topics. In my opinion,
this means that any logic should be covered, but the 'die()' blocks in error
cases do not need to be covered.

It is important to not measure the coverage of the codebase by what old code
is not covered. To help, I created the 'contrib/coverage-diff.sh' script.
After creating the coverage statistics at a version (say, 'topic') you can
then run

    contrib/coverage-diff.sh base topic

to see the lines added between 'base' and 'topic' that are not covered by the
test suite. The output uses 'git blame -c' format so you can find the commits
responsible and view the line numbers for quick access to the context.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 contrib/coverage-diff.sh | 70 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100755 contrib/coverage-diff.sh

diff --git a/contrib/coverage-diff.sh b/contrib/coverage-diff.sh
new file mode 100755
index 0000000000..22acb13d38
--- /dev/null
+++ b/contrib/coverage-diff.sh
@@ -0,0 +1,70 @@
+#!/bin/bash
+
+# Usage: 'contrib/coverage-diff.sh <version1> <version2>
+# Outputs a list of new lines in version2 compared to version1 that are
+# not covered by the test suite. Assumes you ran
+# 'make coverage-test coverage-report' from root first, so .gcov files exist.
+
+V1=$1
+V2=$2
+
+diff-lines() {
+    local path=
+    local line=
+    while read; do
+	esc=$'\033'
+	if [[ $REPLY =~ ---\ (a/)?.* ]]; then
+	    continue
+	elif [[ $REPLY =~ \+\+\+\ (b/)?([^[:blank:]$esc]+).* ]]; then
+	    path=${BASH_REMATCH[2]}
+	elif [[ $REPLY =~ @@\ -[0-9]+(,[0-9]+)?\ \+([0-9]+)(,[0-9]+)?\ @@.* ]]; then
+	    line=${BASH_REMATCH[2]}
+	elif [[ $REPLY =~ ^($esc\[[0-9;]+m)*([\ +-]) ]]; then
+	    echo "$path:$line:$REPLY"
+	    if [[ ${BASH_REMATCH[2]} != - ]]; then
+		((line++))
+	    fi
+	fi
+    done
+}
+
+git diff --raw $V1 $V2 | grep \.c$ | awk 'NF>1{print $NF}' >files.txt
+
+for file in $(cat files.txt)
+do
+	hash_file=${file//\//\#}
+
+	git diff $V1 $V2 -- $file \
+		| diff-lines \
+		| grep ":+" \
+		>"diff_file.txt"
+
+	cat diff_file.txt \
+		| sed -E 's/:/ /g' \
+		| awk '{print $2}' \
+		| sort \
+		>new_lines.txt
+
+	cat "$hash_file.gcov" \
+		| grep \#\#\#\#\# \
+		| sed 's/    #####: //g' \
+		| sed 's/\:/ /g' \
+		| awk '{print $1}' \
+		| sort \
+		>uncovered_lines.txt
+
+	comm -12 uncovered_lines.txt new_lines.txt \
+		| sed -e 's/$/\)/' \
+		| sed -e 's/^/\t/' \
+		>uncovered_new_lines.txt
+
+	grep -q '[^[:space:]]' < uncovered_new_lines.txt && \
+		echo $file && \
+		git blame -c $file \
+			| grep -f uncovered_new_lines.txt
+
+	rm -f diff_file.txt new_lines.txt \
+		uncovered_lines.txt uncovered_new_lines.txt
+done
+
+rm -rf files.txt
-- 
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