update generation in case no tag is found

Signed-off-by: Mike Marchetti <mmarchetti@sandvine.com>

tools/generatechangelog-pipeline.sh

 #!/bin/bash
 
 REPO_NAME=$(basename $(git config --get remote.origin.url) | cut -d'.' -f1)
+git pull --tags origin master &> /dev/null
+
+echo "<h1>$REPO_NAME Changelog</h1>"
 # get the latest tag
 TAG_START=$(git tag | sort -Vr | head -1)
 
-head_tag_diff=$(git rev-list $TAG_START ^HEAD |wc -l)
-if  [ $head_tag_diff -eq 0 ]; then
-    # HEAD and latest tag intersect. Instead try and find a previous tag and use that as the start diff
-    TAG_END=$TAG_START
-    TAG_START=$(git tag | sort -Vr | head -2 | sort -V | head -1)
+# check to see if there is a tag start first.
+if [ ! -z "${TAG_START}" ]; then
+    head_tag_diff=$(git rev-list HEAD ^${TAG_START} |wc -l)
+    if  [ $head_tag_diff -eq 0 ]; then
+        # HEAD and latest tag intersect. Instead try and find a previous tag and use that as the start diff
+        TAG_END=$TAG_START
+        TAG_START=$(git tag | sort -Vr | head -2 | sort -V | head -1)
+    else
+        TAG_END="HEAD"
+    fi
+
+    echo "<h2>tag: ${TAG_START} -> ${TAG_END}</h2>"
+    git log --pretty=format:"<li> <a href=https://osm.etsi.org/gitweb/?p=osm/$REPO_NAME.git;a=commitdiff;h=%H>%h &bull;</a> %s</li> " --reverse  ${TAG_START}..${TAG_END}
 else
-    TAG_END="HEAD"
+    # no tag, just give the full log
+    git log --pretty=format:"<li> <a href=https://osm.etsi.org/gitweb/?p=osm/$REPO_NAME.git;a=commitdiff;h=%H>%h &bull;</a> %s</li> " --reverse
 fi
 
-git pull --tags origin master &> /dev/null
-echo "<h1>$REPO_NAME Changelog</h1>"
-echo "<h2>tag: ${TAG_START} -> ${TAG_END}</h2>"
-git log --pretty=format:"<li> <a href=https://osm.etsi.org/gitweb/?p=osm/$REPO_NAME.git;a=commitdiff;h=%H>%h &bull;</a> %s</li> " --reverse  ${TAG_START}..${TAG_END}