Fix `shellcheck` lints of our various bash scripts

The following lints have been fixed:
SC2046,SC2086,SC2068,SC2148,SC2007,SC2004,SC2006,
SC2164,SC2145,SC1091,SC2034,SC2155.

6 files changed, 16 insertions, 11 deletions

diff --git a/android/docs/diagrams/update_graphs.sh b/android/docs/diagrams/update_graphs.sh
index 51d3b74b85..c339cdeac1 100755
--- a/android/docs/diagrams/update_graphs.sh
+++ b/android/docs/diagrams/update_graphs.sh
@@ -2,4 +2,4 @@
 
 SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
 
-plantuml $SCRIPT_DIR/*.puml
+plantuml "$SCRIPT_DIR"/*.puml
diff --git a/android/fdroid-build/env.sh b/android/fdroid-build/env.sh
index 3e2faf8fe2..c6c3e224b6 100755
--- a/android/fdroid-build/env.sh
+++ b/android/fdroid-build/env.sh
@@ -1,6 +1,8 @@
+#!/usr/bin/env bash
 # Sourcing this file prepares the environment for building inside the F-Droid build server
 
 # Ensure Cargo tools are accessible
+# shellcheck source=/dev/null
 source "$HOME/.cargo/env"
 
 # Ensure Go compiler is accessible
diff --git a/android/fdroid-build/init.sh b/android/fdroid-build/init.sh
index 4d5cf8ce35..07bc5939d7 100755
--- a/android/fdroid-build/init.sh
+++ b/android/fdroid-build/init.sh
@@ -5,12 +5,12 @@ set -eux
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
 REPO_DIR="$SCRIPT_DIR/../../"
-TOOLCHAINS_DIR="$HOME/android-ndk-toolchains"
 
 # Install Rust
 curl -sf -L https://sh.rustup.rs > /tmp/rustup.sh
 chmod +x /tmp/rustup.sh
 /tmp/rustup.sh -y
+# shellcheck source=/dev/null
 source "$HOME/.cargo/env"
 rustup set profile minimal
 rustup target add \
diff --git a/android/scripts/generate-pngs.sh b/android/scripts/generate-pngs.sh
index 6aa4aa380e..dc72e9f538 100755
--- a/android/scripts/generate-pngs.sh
+++ b/android/scripts/generate-pngs.sh
@@ -46,11 +46,12 @@ function convert_image() {
 
     local source_image="$1"
     local dpi_config="$2"
+    local destination_image
 
     if (( $# >= 3 )); then
-        local destination_image="$3"
+        destination_image="$3"
     else
-        local destination_image="$(basename "$source_image" .svg | sed -e 's/-/_/g')"
+        destination_image="$(basename "$source_image" .svg | sed -e 's/-/_/g')"
     fi
 
     if (( $# >= 4 )); then
@@ -59,8 +60,10 @@ function convert_image() {
         local destination_dir="drawable"
     fi
 
-    local dpi="$(echo "$dpi_config" | cut -f1 -d'-')"
-    local size="$(echo "$dpi_config" | cut -f2 -d'-')"
+    local dpi
+    dpi="$(echo "$dpi_config" | cut -f1 -d'-')"
+    local size
+    size="$(echo "$dpi_config" | cut -f2 -d'-')"
 
     local dpi_dir="../lib/resource/src/main/res/${destination_dir}-${dpi}"
 
diff --git a/android/scripts/run-instrumented-tests-locally.sh b/android/scripts/run-instrumented-tests-locally.sh
index 359c648d30..4a642356eb 100755
--- a/android/scripts/run-instrumented-tests-locally.sh
+++ b/android/scripts/run-instrumented-tests-locally.sh
@@ -4,7 +4,7 @@ set -eu
 
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
-cd $SCRIPT_DIR/..
+cd "$SCRIPT_DIR"/..
 ./gradlew assembleOssProdAndroidTest
 ./gradlew app:assembleOssProdDebug
-$SCRIPT_DIR/run-instrumented-tests.sh app
+"$SCRIPT_DIR"/run-instrumented-tests.sh app
diff --git a/android/scripts/run-instrumented-tests.sh b/android/scripts/run-instrumented-tests.sh
index 5e3320533f..e72d4687bd 100755
--- a/android/scripts/run-instrumented-tests.sh
+++ b/android/scripts/run-instrumented-tests.sh
@@ -23,7 +23,7 @@ INVALID_TEST_ACCOUNT_TOKEN="${INVALID_TEST_ACCOUNT_TOKEN:-}"
 while [[ "$#" -gt 0 ]]; do
     case $1 in
         --test-type)
-            if [[ ! -z ${2-} && "$2" =~ ^(app|mockapi|e2e)$ ]]; then
+            if [[ -n "${2-}" && "$2" =~ ^(app|mockapi|e2e)$ ]]; then
                 TEST_TYPE="$2"
             else
                 echo "Error: Bad or missing test type. Must be one of: app, mockapi, e2e"
@@ -32,7 +32,7 @@ while [[ "$#" -gt 0 ]]; do
             shift 2
             ;;
         --infra-flavor)
-            if [[ ! -z ${2-} && "$2" =~ ^(prod|stagemole)$ ]]; then
+            if [[ -n "${2-}" && "$2" =~ ^(prod|stagemole)$ ]]; then
                 INFRA_FLAVOR="$2"
             else
                 echo "Error: Bad or missing infra flavor. Must be one of: prod, stagemole"
@@ -41,7 +41,7 @@ while [[ "$#" -gt 0 ]]; do
             shift 2
             ;;
         --billing-flavor)
-            if [[ ! -z ${2-} && "$2" =~ ^(oss|play)$ ]]; then
+            if [[ -n "${2-}" && "$2" =~ ^(oss|play)$ ]]; then
                 BILLING_FLAVOR="$2"
             else
                 echo "Error: Bad or missing billing flavor. Must be one of: oss, play"