internal/postgres: check parsing errors & fix patch parsing

This CL adds error checking for the semver parsing in InsertVersion.
It also fixes patch parsing so that it properly isolates the number
string when there is a prerelease.

Fixes b/129717943

Change-Id: I542b533d9508027917b1f9fa63867607b31d23fc
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/443170
Reviewed-by: Julie Qiu <julieqiu@google.com>

internal/postgres/postgres.go

@@ -470,12 +470,21 @@ func (db *DB) InsertVersion(version *internal.Version) error {
 		}
 
 		versionSplit := strings.Split(version.Version, ".")
-		major, _ := strconv.ParseInt(strings.TrimPrefix("v", versionSplit[0]), 0, 64)
-		minor, _ := strconv.ParseInt(versionSplit[1], 0, 64)
-		patch, _ := strconv.ParseInt(strings.Split(versionSplit[2], semver.Prerelease(version.Version))[0], 0, 64)
+		major, err := strconv.Atoi(strings.TrimPrefix(versionSplit[0], "v"))
+		if err != nil {
+			return fmt.Errorf("strconv.Atoi(%q): %v", strings.TrimPrefix(versionSplit[0], "v"), err)
+		}
+		minor, err := strconv.Atoi(versionSplit[1])
+		if err != nil {
+			return fmt.Errorf("strconv.Atoi(%q): %v", versionSplit[1], err)
+		}
+		patch, err := strconv.Atoi(strings.Split(versionSplit[2], "-")[0])
+		if err != nil {
+			return fmt.Errorf("strconv.Atoi(%q): %v", strings.Split(versionSplit[2], "-")[0], err)
+		}
 		prerelease, err := padPrerelease(semver.Prerelease(version.Version))
 		if err != nil {
-			return fmt.Errorf("error padding prerelease: %v", err)
+			return fmt.Errorf("padPrerelease(%q): %v", semver.Prerelease(version.Version), err)
 		}
 
 		if _, err := tx.Exec(