From 01cffddffa5bfda9cc11892dd288101291b38291 Mon Sep 17 00:00:00 2001
From: Christian Kreibich <christian@corelight.com>
Date: Wed, 7 Oct 2020 15:56:29 -0700
Subject: [PATCH 1/4] Consistent indentation for btest-diff, no other changes

---
 btest-diff | 108 ++++++++++++++++++++++++++---------------------------
 1 file changed, 54 insertions(+), 54 deletions(-)

diff --git a/btest-diff b/btest-diff
index 72557d6b..601b3e9a 100755
--- a/btest-diff
+++ b/btest-diff
@@ -25,8 +25,8 @@ if [ "$TEST_DIAGNOSTICS" = "" ]; then
 fi
 
 if [ "$#" -lt 1 ]; then
-   echo "btest-diff: wrong number of arguments" >$TEST_DIAGNOSTICS
-   exit 1
+    echo "btest-diff: wrong number of arguments" >$TEST_DIAGNOSTICS
+    exit 1
 fi
 
 input=$1
@@ -34,13 +34,13 @@ canon=`echo $input | sed 's#/#.#g'`
 shift
 
 if [ ! -f $input ]; then
-   echo "btest-diff: input $input does not exist." >$TEST_DIAGNOSTICS
-   exit 1
+    echo "btest-diff: input $input does not exist." >$TEST_DIAGNOSTICS
+    exit 1
 fi
 
 tmpfiles=""
 function delete_tmps {
-     rm -f $tmpfiles 2>/dev/null
+    rm -f $tmpfiles 2>/dev/null
 }
 
 trap delete_tmps 0
@@ -65,70 +65,70 @@ else
 fi
 
 if [ -e $TEST_BASELINE/$canon ]; then
-   error=0
-
-   if [ "$TEST_DIFF_CANONIFIER" != "" ]; then
-       diff1=/tmp/test-diff.$$.$canon.baseline.tmp
-       diff2=/tmp/test-diff.$$.$canon.tmp
-       tmpfiles="$tmpfiles $diff1 $diff2"
-
-       eval $TEST_DIFF_CANONIFIER $TEST_BASELINE/$canon <$TEST_BASELINE/$canon >$diff1
-       if [ $? -ne 0 ]; then
-           error=1
-           echo "== Error ==============================" >>$TEST_DIAGNOSTICS
-           echo "btest-diff: TEST_DIFF_CANONIFIER failed on file '$TEST_BASELINE/$canon'" >>$TEST_DIAGNOSTICS
-           result=1
-       fi
-
-       eval $TEST_DIFF_CANONIFIER $input <$input >$diff2
-       if [ $? -ne 0 ]; then
-           error=1
-           echo "== Error ==============================" >>$TEST_DIAGNOSTICS
-           echo "btest-diff: TEST_DIFF_CANONIFIER failed on file '$input'" >>$TEST_DIAGNOSTICS
-           result=1
-       fi
-   else
-       diff1=$TEST_BASELINE/$canon
-       diff2=$input
-   fi
-
-   if [ $error -eq 0 ]; then
-       echo "== Diff ===============================" >>$TEST_DIAGNOSTICS
-       diff -au $@ $diff1 $diff2 >>$TEST_DIAGNOSTICS
-       result=$?
-   fi
+    error=0
+
+    if [ "$TEST_DIFF_CANONIFIER" != "" ]; then
+        diff1=/tmp/test-diff.$$.$canon.baseline.tmp
+        diff2=/tmp/test-diff.$$.$canon.tmp
+        tmpfiles="$tmpfiles $diff1 $diff2"
+
+        eval $TEST_DIFF_CANONIFIER $TEST_BASELINE/$canon <$TEST_BASELINE/$canon >$diff1
+        if [ $? -ne 0 ]; then
+            error=1
+            echo "== Error ==============================" >>$TEST_DIAGNOSTICS
+            echo "btest-diff: TEST_DIFF_CANONIFIER failed on file '$TEST_BASELINE/$canon'" >>$TEST_DIAGNOSTICS
+            result=1
+        fi
+
+        eval $TEST_DIFF_CANONIFIER $input <$input >$diff2
+        if [ $? -ne 0 ]; then
+            error=1
+            echo "== Error ==============================" >>$TEST_DIAGNOSTICS
+            echo "btest-diff: TEST_DIFF_CANONIFIER failed on file '$input'" >>$TEST_DIAGNOSTICS
+            result=1
+        fi
+    else
+        diff1=$TEST_BASELINE/$canon
+        diff2=$input
+    fi
+
+    if [ $error -eq 0 ]; then
+        echo "== Diff ===============================" >>$TEST_DIAGNOSTICS
+        diff -au $@ $diff1 $diff2 >>$TEST_DIAGNOSTICS
+        result=$?
+    fi
 else
-   echo "== Error ==============================" >>$TEST_DIAGNOSTICS
-   echo "test-diff: no baseline found." >>$TEST_DIAGNOSTICS
-   result=100
+    echo "== Error ==============================" >>$TEST_DIAGNOSTICS
+    echo "test-diff: no baseline found." >>$TEST_DIAGNOSTICS
+    result=100
 fi
 
 echo "=======================================" >>$TEST_DIAGNOSTICS
 
 if [ "$TEST_MODE" == "TEST" ]; then
-   exit $result
+    exit $result
 
 elif [ "$TEST_MODE" == "UPDATE_INTERACTIVE" ]; then
 
-   if [ "$result" == 0 ]; then
-       exit 0
-   fi
+    if [ "$result" == 0 ]; then
+        exit 0
+    fi
 
-   btest-ask-update
-   rc=$?
+    btest-ask-update
+    rc=$?
 
-   echo -n "$TEST_NAME ..." >/dev/tty
+    echo -n "$TEST_NAME ..." >/dev/tty
 
-   if [ $rc == 0 ]; then
-       cp $input $TEST_BASELINE/$canon
-       exit 0
-   fi
+    if [ $rc == 0 ]; then
+        cp $input $TEST_BASELINE/$canon
+        exit 0
+    fi
 
-   exit $rc
+    exit $rc
 
 elif [ "$TEST_MODE" == "UPDATE" ]; then
-   cp $input $TEST_BASELINE/$canon
-   exit 0
+    cp $input $TEST_BASELINE/$canon
+    exit 0
 fi
 
 echo "test-diff: unknown test mode $TEST_MODE" >$TEST_DIAGNOSTICS

From 7a6b5e0bddd01c7029017624c76208ecf4b71bb7 Mon Sep 17 00:00:00 2001
From: Christian Kreibich <christian@corelight.com>
Date: Sat, 3 Oct 2020 23:34:59 -0700
Subject: [PATCH 2/4] Canonify outputs when updating baselines via btest-diff

This leverages the same canonicalization btest-diff already applies
during test output comparison against baselines also when updating
those baselines (usually via btest -U/-u). This removes a bunch of
noise from the baselines, including personal home directories,
timestamps, etc.

Since btest-diff doesn't know whether the baseline has undergone this
canonicalization, it continues to canonicalize the basline prior to
diffing. To track whether it has canonicalized a baseline when
updating, btest-diff now also prepends a header to the generated
baseline that warns users about the fact that it is
auto-generated. The presence of this header doubles as a marker for
canonicalization.

Includes a test-case.
---
 btest-diff                               | 100 ++++++++++++++++++-----
 testing/tests/canonifier-conversion.test |  52 ++++++++++++
 2 files changed, 130 insertions(+), 22 deletions(-)
 create mode 100644 testing/tests/canonifier-conversion.test

diff --git a/btest-diff b/btest-diff
index 601b3e9a..9648b3cc 100755
--- a/btest-diff
+++ b/btest-diff
@@ -16,6 +16,41 @@
 # Maximum number of lines to show from mismatching input file by default.
 MAX_LINES=100
 
+# Header line we tuck onto new baselines generated by
+# btest-diff. Serves both as a warning and as an indicator that the
+# baseline has been run through the TEST_DIFF_CANONIFIER (if any).
+HEADER="### btest baseline data generated by btest-diff. Do not edit. Use btest -U/-u to update."
+
+# Predicate, succeeds if the given baseline is canonicalized.
+function is_canon_baseline {
+    local input="$1"
+
+    if head -1 "$input" | grep -q -F "$HEADER" 2>/dev/null; then
+        return 0
+    fi
+
+    return 1
+}
+
+# Prints the requested baseline to standard out if it is
+# canonicalized. Otherwise, fails.
+function get_canon_baseline {
+    local input="$1"
+
+    ! is_canon_baseline "$input" && return 1
+    tail -n +2 "$input"
+}
+
+# Updates the given baseline to the given destination, prepending our
+# header.
+function update_canon_baseline {
+    local input="$1"
+    local output="$2"
+
+    echo "$HEADER" >"$output"
+    cat "$input" >>"$output"
+}
+
 if [ -n "$TEST_DIFF_FILE_MAX_LINES" ]; then
     MAX_LINES=$TEST_DIFF_FILE_MAX_LINES
 fi
@@ -64,40 +99,49 @@ else
     fi
 fi
 
-if [ -e $TEST_BASELINE/$canon ]; then
-    error=0
+# If no canonifier is defined, just copy. Simplifies code layout.
+if [ -z "$TEST_DIFF_CANONIFIER" ]; then
+    TEST_DIFF_CANONIFIER="cat"
+fi
 
-    if [ "$TEST_DIFF_CANONIFIER" != "" ]; then
-        diff1=/tmp/test-diff.$$.$canon.baseline.tmp
-        diff2=/tmp/test-diff.$$.$canon.tmp
-        tmpfiles="$tmpfiles $diff1 $diff2"
+canon_output=/tmp/test-diff.$$.$canon.tmp
+tmpfiles="$tmpfiles $canon_output"
+error=0
 
-        eval $TEST_DIFF_CANONIFIER $TEST_BASELINE/$canon <$TEST_BASELINE/$canon >$diff1
+# Canonicalize the new test output.
+eval "$TEST_DIFF_CANONIFIER" "$input" <"$input" >"$canon_output"
+if [ $? -ne 0 ]; then
+    echo "== Error ==============================" >>$TEST_DIAGNOSTICS
+    echo "btest-diff: TEST_DIFF_CANONIFIER failed on file '$input'" >>$TEST_DIAGNOSTICS
+    error=1
+    result=1
+fi
+
+if [ -e $TEST_BASELINE/$canon ]; then
+    canon_baseline=/tmp/test-diff.$$.$canon.baseline.tmp
+    tmpfiles="$tmpfiles $canon_baseline"
+
+    # Prepare the baseline. When created by a recent btest-diff, we
+    # don't need to re-canonicalize, otherwise we do.
+    if ! get_canon_baseline $TEST_BASELINE/$canon >$canon_baseline; then
+        # It's an older uncanonicalized baseline, so canonicalize
+        # it now prior to comparison. Future updates via btest
+        # -U/-u will then store it canonicalized.
+        eval $TEST_DIFF_CANONIFIER <$TEST_BASELINE/$canon >$canon_baseline
         if [ $? -ne 0 ]; then
-            error=1
             echo "== Error ==============================" >>$TEST_DIAGNOSTICS
             echo "btest-diff: TEST_DIFF_CANONIFIER failed on file '$TEST_BASELINE/$canon'" >>$TEST_DIAGNOSTICS
-            result=1
-        fi
-
-        eval $TEST_DIFF_CANONIFIER $input <$input >$diff2
-        if [ $? -ne 0 ]; then
             error=1
-            echo "== Error ==============================" >>$TEST_DIAGNOSTICS
-            echo "btest-diff: TEST_DIFF_CANONIFIER failed on file '$input'" >>$TEST_DIAGNOSTICS
             result=1
         fi
-    else
-        diff1=$TEST_BASELINE/$canon
-        diff2=$input
     fi
 
     if [ $error -eq 0 ]; then
         echo "== Diff ===============================" >>$TEST_DIAGNOSTICS
-        diff -au $@ $diff1 $diff2 >>$TEST_DIAGNOSTICS
+        diff -au $@ $canon_baseline $canon_output >>$TEST_DIAGNOSTICS
         result=$?
     fi
-else
+elif [ "$TEST_MODE" = "TEST" ]; then
     echo "== Error ==============================" >>$TEST_DIAGNOSTICS
     echo "test-diff: no baseline found." >>$TEST_DIAGNOSTICS
     result=100
@@ -110,6 +154,12 @@ if [ "$TEST_MODE" == "TEST" ]; then
 
 elif [ "$TEST_MODE" == "UPDATE_INTERACTIVE" ]; then
 
+    # We had a problem running the canonifier
+    if [ "$error" != 0 ]; then
+        exit 1
+    fi
+
+    # There's no change to the baseline, so skip user interaction
     if [ "$result" == 0 ]; then
         exit 0
     fi
@@ -120,14 +170,20 @@ elif [ "$TEST_MODE" == "UPDATE_INTERACTIVE" ]; then
     echo -n "$TEST_NAME ..." >/dev/tty
 
     if [ $rc == 0 ]; then
-        cp $input $TEST_BASELINE/$canon
+        update_canon_baseline $canon_output $TEST_BASELINE/$canon
         exit 0
     fi
 
     exit $rc
 
 elif [ "$TEST_MODE" == "UPDATE" ]; then
-    cp $input $TEST_BASELINE/$canon
+
+    # We had a problem running the canonifier
+    if [ "$error" != 0 ]; then
+        exit 1
+    fi
+
+    update_canon_baseline $canon_output $TEST_BASELINE/$canon
     exit 0
 fi
 
diff --git a/testing/tests/canonifier-conversion.test b/testing/tests/canonifier-conversion.test
new file mode 100644
index 00000000..c1c0e486
--- /dev/null
+++ b/testing/tests/canonifier-conversion.test
@@ -0,0 +1,52 @@
+# This test verifies that we only canonicalize baselines once, namely
+# when canonicalizing new test output, and that baselines get
+# converted over to our header-tagged format.
+#
+# Test prep: make our canonifier executable
+# %TEST-EXEC: chmod 755 ./diff-double-x
+#
+# Verify that without an existing baseline, we canonify a new one.
+# %TEST-EXEC: btest -U %INPUT
+# %TEST-EXEC: head -1 Baseline/canonifier-conversion/output | grep -q 'Do not edit'
+# %TEST-EXEC: tail -1 Baseline/canonifier-conversion/output | grep xx
+# %TEST-EXEC: cp Baseline/canonifier-conversion/output base.1
+#
+# For testing conversion, first create a "dated" baseline.
+# %TEST-EXEC: echo x >Baseline/canonifier-conversion/output
+#
+# Verify that it succeeds:
+# %TEST-EXEC: btest %INPUT
+#
+# Update the baseline. This should prefix btest-diff's header and canonify:
+# %TEST-EXEC: btest -U %INPUT
+#
+# Verify that these have happened and preserve baseline:
+# %TEST-EXEC: head -1 Baseline/canonifier-conversion/output | grep -q 'Do not edit'
+# %TEST-EXEC: tail -1 Baseline/canonifier-conversion/output | grep xx
+# %TEST-EXEC: cp Baseline/canonifier-conversion/output base.2
+#
+# Verify that it still succeeds:
+# %TEST-EXEC: btest %INPUT
+#
+# Update the baseline again.
+# %TEST-EXEC: btest -U %INPUT
+# %TEST-EXEC: cp Baseline/canonifier-conversion/output base.3
+#
+# Verify the updated baselines remained identical.
+# %TEST-EXEC: test "$(cat base.1)" = "$(cat base.2)" && test "$(cat base.2)" = "$(cat base.3)"
+
+@TEST-EXEC: echo x >output
+@TEST-EXEC: btest-diff output
+
+%TEST-START-FILE btest.cfg
+[btest]
+TmpDir      = .tmp
+
+[environment]
+TEST_DIFF_CANONIFIER=%(testbase)s/diff-double-x
+%TEST-END-FILE
+
+%TEST-START-FILE diff-double-x
+#! /usr/bin/env bash
+sed 's/x/xx/g'
+%TEST-END-FILE

From 0ab5004e9668f2632eb6f0f55e120dc7c04234a1 Mon Sep 17 00:00:00 2001
From: Christian Kreibich <christian@corelight.com>
Date: Wed, 7 Oct 2020 16:25:23 -0700
Subject: [PATCH 3/4] A shellcheck pass on btest-diff

---
 btest-diff | 53 +++++++++++++++++++++++++++++------------------------
 1 file changed, 29 insertions(+), 24 deletions(-)

diff --git a/btest-diff b/btest-diff
index 9648b3cc..79d44c04 100755
--- a/btest-diff
+++ b/btest-diff
@@ -12,6 +12,9 @@
 #   TEST_DIFF_CANONIFIER
 #   TEST_DIFF_BRIEF
 #   TEST_DIFF_FILE_MAX_LINES
+#
+# It's okay to check $? explicitly:
+# shellcheck disable=SC2181
 
 # Maximum number of lines to show from mismatching input file by default.
 MAX_LINES=100
@@ -22,10 +25,10 @@ MAX_LINES=100
 HEADER="### btest baseline data generated by btest-diff. Do not edit. Use btest -U/-u to update."
 
 # Predicate, succeeds if the given baseline is canonicalized.
-function is_canon_baseline {
+is_canon_baseline() {
     local input="$1"
 
-    if head -1 "$input" | grep -q -F "$HEADER" 2>/dev/null; then
+    if head -n 1 "$input" | grep -q -F "$HEADER" 2>/dev/null; then
         return 0
     fi
 
@@ -34,7 +37,7 @@ function is_canon_baseline {
 
 # Prints the requested baseline to standard out if it is
 # canonicalized. Otherwise, fails.
-function get_canon_baseline {
+get_canon_baseline() {
     local input="$1"
 
     ! is_canon_baseline "$input" && return 1
@@ -43,7 +46,7 @@ function get_canon_baseline {
 
 # Updates the given baseline to the given destination, prepending our
 # header.
-function update_canon_baseline {
+update_canon_baseline() {
     local input="$1"
     local output="$2"
 
@@ -64,17 +67,18 @@ if [ "$#" -lt 1 ]; then
     exit 1
 fi
 
-input=$1
-canon=`echo $input | sed 's#/#.#g'`
+input="$1"
+# shellcheck disable=SC2001
+canon=$(echo "$input" | sed 's#/#.#g')
 shift
 
-if [ ! -f $input ]; then
+if [ ! -f "$input" ]; then
     echo "btest-diff: input $input does not exist." >$TEST_DIAGNOSTICS
     exit 1
 fi
 
 tmpfiles=""
-function delete_tmps {
+delete_tmps() {
     rm -f $tmpfiles 2>/dev/null
 }
 
@@ -86,15 +90,15 @@ rm -f $TEST_DIAGNOSTICS  2>/dev/null
 
 echo "== File ===============================" >>$TEST_DIAGNOSTICS
 
-if [ ! -e $TEST_BASELINE/$canon ]; then
-    cat $input >>$TEST_DIAGNOSTICS
+if [ ! -e "$TEST_BASELINE/$canon" ]; then
+    cat "$input" >>$TEST_DIAGNOSTICS
 elif [ -n "$TEST_DIFF_BRIEF" ]; then
     echo "<Content not shown>" >>$TEST_DIAGNOSTICS
 else
-    if [ `wc -l $input | awk '{print $1}'` -le $MAX_LINES ]; then
-        cat $input >>$TEST_DIAGNOSTICS
+    if [ "$(wc -l "$input" | awk '{print $1}')" -le "$MAX_LINES" ]; then
+        cat "$input" >>$TEST_DIAGNOSTICS
     else
-        head -$MAX_LINES $input >>$TEST_DIAGNOSTICS
+        head -n "$MAX_LINES" "$input" >>$TEST_DIAGNOSTICS
         echo "[... File too long, truncated ...]" >>$TEST_DIAGNOSTICS
     fi
 fi
@@ -109,6 +113,7 @@ tmpfiles="$tmpfiles $canon_output"
 error=0
 
 # Canonicalize the new test output.
+# shellcheck disable=SC2094
 eval "$TEST_DIFF_CANONIFIER" "$input" <"$input" >"$canon_output"
 if [ $? -ne 0 ]; then
     echo "== Error ==============================" >>$TEST_DIAGNOSTICS
@@ -117,17 +122,17 @@ if [ $? -ne 0 ]; then
     result=1
 fi
 
-if [ -e $TEST_BASELINE/$canon ]; then
+if [ -e "$TEST_BASELINE/$canon" ]; then
     canon_baseline=/tmp/test-diff.$$.$canon.baseline.tmp
     tmpfiles="$tmpfiles $canon_baseline"
 
     # Prepare the baseline. When created by a recent btest-diff, we
     # don't need to re-canonicalize, otherwise we do.
-    if ! get_canon_baseline $TEST_BASELINE/$canon >$canon_baseline; then
+    if ! get_canon_baseline "$TEST_BASELINE/$canon" >"$canon_baseline"; then
         # It's an older uncanonicalized baseline, so canonicalize
         # it now prior to comparison. Future updates via btest
         # -U/-u will then store it canonicalized.
-        eval $TEST_DIFF_CANONIFIER <$TEST_BASELINE/$canon >$canon_baseline
+        eval "$TEST_DIFF_CANONIFIER" <"$TEST_BASELINE/$canon" >"$canon_baseline"
         if [ $? -ne 0 ]; then
             echo "== Error ==============================" >>$TEST_DIAGNOSTICS
             echo "btest-diff: TEST_DIFF_CANONIFIER failed on file '$TEST_BASELINE/$canon'" >>$TEST_DIAGNOSTICS
@@ -138,7 +143,7 @@ if [ -e $TEST_BASELINE/$canon ]; then
 
     if [ $error -eq 0 ]; then
         echo "== Diff ===============================" >>$TEST_DIAGNOSTICS
-        diff -au $@ $canon_baseline $canon_output >>$TEST_DIAGNOSTICS
+        diff -au "$@" "$canon_baseline" "$canon_output" >>$TEST_DIAGNOSTICS
         result=$?
     fi
 elif [ "$TEST_MODE" = "TEST" ]; then
@@ -149,10 +154,10 @@ fi
 
 echo "=======================================" >>$TEST_DIAGNOSTICS
 
-if [ "$TEST_MODE" == "TEST" ]; then
+if [ "$TEST_MODE" = "TEST" ]; then
     exit $result
 
-elif [ "$TEST_MODE" == "UPDATE_INTERACTIVE" ]; then
+elif [ "$TEST_MODE" = "UPDATE_INTERACTIVE" ]; then
 
     # We had a problem running the canonifier
     if [ "$error" != 0 ]; then
@@ -160,7 +165,7 @@ elif [ "$TEST_MODE" == "UPDATE_INTERACTIVE" ]; then
     fi
 
     # There's no change to the baseline, so skip user interaction
-    if [ "$result" == 0 ]; then
+    if [ "$result" = 0 ]; then
         exit 0
     fi
 
@@ -169,21 +174,21 @@ elif [ "$TEST_MODE" == "UPDATE_INTERACTIVE" ]; then
 
     echo -n "$TEST_NAME ..." >/dev/tty
 
-    if [ $rc == 0 ]; then
-        update_canon_baseline $canon_output $TEST_BASELINE/$canon
+    if [ $rc = 0 ]; then
+        update_canon_baseline "$canon_output" "$TEST_BASELINE/$canon"
         exit 0
     fi
 
     exit $rc
 
-elif [ "$TEST_MODE" == "UPDATE" ]; then
+elif [ "$TEST_MODE" = "UPDATE" ]; then
 
     # We had a problem running the canonifier
     if [ "$error" != 0 ]; then
         exit 1
     fi
 
-    update_canon_baseline $canon_output $TEST_BASELINE/$canon
+    update_canon_baseline "$canon_output" "$TEST_BASELINE/$canon"
     exit 0
 fi
 

From a7b772ca24b275263209c854e1399a3729a14f4e Mon Sep 17 00:00:00 2001
From: Christian Kreibich <christian@corelight.com>
Date: Thu, 8 Oct 2020 12:07:50 -0700
Subject: [PATCH 4/4] Document btest-diff's exit codes

---
 btest-diff | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/btest-diff b/btest-diff
index 79d44c04..05bed144 100755
--- a/btest-diff
+++ b/btest-diff
@@ -13,6 +13,25 @@
 #   TEST_DIFF_BRIEF
 #   TEST_DIFF_FILE_MAX_LINES
 #
+# This script has the following exit codes:
+#
+# When TEST_MODE is TEST:
+# 0 - Comparison succeeded, files are the same
+# 1 - Problems with input file/args or running TEST_DIFF_CANONIFIER, or file contents differ
+# 2 - Other diffing trouble (inherited from diff)
+# 100 - No baseline to compare to available
+#
+# When TEST_MODE is UPDATE:
+# 0 - Baseline updated
+# 1 - Problems with input file/args or running TEST_DIFF_CANONIFIER
+#
+# When TEST_MODE is UPDATE_INTERACTIVE:
+# 0 - Baseline updated, or nothing to update
+# 1 - Problems with input file/args or running TEST_DIFF_CANONIFIER, or user skips a deviating baseline
+# 200 - User asks to abort after a deviating baseline
+#
+# Otherwise: exits with 1
+
 # It's okay to check $? explicitly:
 # shellcheck disable=SC2181